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2008-07-03block: Globalize bio_set and bio_vec_slabMartin K. Petersen
Move struct bio_set and biovec_slab definitions to bio.h so they can be used outside of bio.c. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-07docbook: fix bio missing parameterRandy Dunlap
Fix fs/bio.c kernel-doc parameter warning: Warning(linux-2.6.25-git14//fs/bio.c:972): No description found for parameter 'reading' Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-07block: use unitialized_var() in bio_alloc_bioset()Jens Axboe
Better than setting idx to some random value and it silences the same bogus gcc warning. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-29block: add dma alignment and padding support to blk_rq_map_kernFUJITA Tomonori
This patch adds bio_copy_kern similar to bio_copy_user. blk_rq_map_kern uses bio_copy_kern instead of bio_map_kern if necessary. bio_copy_kern uses temporary pages and the bi_end_io callback frees these pages. bio_copy_kern saves the original kernel buffer at bio->bi_private it doesn't use something like struct bio_map_data to store the information about the caller. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: Tejun Heo <htejun@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-21block: convert bio_copy_user to bio_copy_user_iovFUJITA Tomonori
This patch enables bio_copy_user to take struct sg_iovec (renamed bio_copy_user_iov). bio_copy_user uses bio_copy_user_iov internally as bio_map_user uses bio_map_user_iov. The major changes are: - adds sg_iovec array to struct bio_map_data - adds __bio_copy_iov that copy data between bio and sg_iovec. bio_copy_user_iov and bio_uncopy_user use it. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: Tejun Heo <htejun@gmail.com> Cc: Mike Christie <michaelc@cs.wisc.edu> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-03-17Revert "unexport bio_{,un}map_user"Jens Axboe
Outside users like asmlib uses the mapping functions. API wise, the export is definitely sane. It's a better idea to keep this export than to require external users to open-code this piece of code instead. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-02-19fs/block_dev.c: remove #if 0'ed codeAdrian Bunk
Commit b2e895dbd80c420bfc0937c3729b4afe073b3848 #if 0'ed this code stating: <-- snip --> [PATCH] revert blockdev direct io back to 2.6.19 version Andrew Vasquez is reporting as-iosched oopses and a 65% throughput slowdown due to the recent special-casing of direct-io against blockdevs. We don't know why either of these things are occurring. The patch minimally reverts us back to the 2.6.19 code for a 2.6.20 release. <-- snip --> It has since been dead code, and unless someone wants to revive it now it's time to remove it. This patch also makes bio_release_pages() static again and removes the ki_bio_count member from struct kiocb, reverting changes that had been done for this dead code. Signed-off-by: Adrian Bunk <bunk@kernel.org> Signed-off-by: Jens Axboe <axboe@carl.home.kernel.dk>
2008-01-28__bio_clone: don't calculate hw/phys segment countsJens Axboe
If the users sets a new ->bi_bdev on the bio after __bio_clone() has returned it, the "segment counts valid" flag still remains even though it may be different with the new target. So don't calculate segment counts in __bio_clone(). Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-16bio: make freeing of ->bi_io_vec conditional in bio_free()Jens Axboe
The empty barrier patches do not carry data, so they have no iovec attached. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-16bio: use memset() in bio_init()Jens Axboe
Use memset() to clear the bio, instead of doing each field manually. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-10Drop 'size' argument from bio_endio and bi_end_ioNeilBrown
As bi_end_io is only called once when the reqeust is complete, the 'size' argument is now redundant. Remove it. Now there is no need for bio_endio to subtract the size completed from bi_size. So don't do that either. While we are at it, change bi_end_io to return void. Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-10Don't decrement bi_size in bio_endioNeilBrown
The only caller of bio_endio that does not pass the full bi_size is end_that_request_first. Also, no ->bi_end_io method is really interested in bi_size being decremented. So move the decrement and related code into ll_rw_blk and merge it with order_bio_endio to form req_bio_endio which does endio functionality specific to request completion. As some ->bi_end_io methods do check bi_size of 0, we set it thus for now, but that will go in the next patch. Signed-off-by: Neil Brown <neilb@suse.de> ### Diffstat output ./block/ll_rw_blk.c | 42 +++++++++++++++++++++++++++--------------- ./fs/bio.c | 23 +++++++++++------------ 2 files changed, 38 insertions(+), 27 deletions(-) diff .prev/block/ll_rw_blk.c ./block/ll_rw_blk.c Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-10Only call bi_end_io once for any bioNeilBrown
Currently bi_end_io can be called multiple times as sub-requests complete. However no ->bi_end_io function wants to know about that. So only call when the bio is complete. Signed-off-by: Neil Brown <neilb@suse.de> ### Diffstat output ./fs/bio.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff .prev/fs/bio.c ./fs/bio.c Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-24[BLOCK] Get rid of request_queue_t typedefJens Axboe
Some of the code has been gradually transitioned to using the proper struct request_queue, but there's lots left. So do a full sweet of the kernel and get rid of this typedef and replace its uses with the proper type. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-20mm: Remove slab destructors from kmem_cache_create().Paul Mundt
Slab destructors were no longer supported after Christoph's c59def9f222d44bb7e2f0a559f2906191a0862d7 change. They've been BUGs for both slab and slub, and slob never supported them either. This rips out support for the dtor pointer from kmem_cache_create() completely and fixes up every single callsite in the kernel (there were about 224, not including the slab allocator definitions themselves, or the documentation references). Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2007-07-10unexport bio_{,un}map_userAdrian Bunk
bio_{,un}map_user no longer have any modular users. Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-05-07KMEM_CACHE(): simplify slab cache creationChristoph Lameter
This patch provides a new macro KMEM_CACHE(<struct>, <flags>) to simplify slab creation. KMEM_CACHE creates a slab with the name of the struct, with the size of the struct and with the alignment of the struct. Additional slab flags may be specified if necessary. Example struct test_slab { int a,b,c; struct list_head; } __cacheline_aligned_in_smp; test_slab_cache = KMEM_CACHE(test_slab, SLAB_PANIC) will create a new slab named "test_slab" of the size sizeof(struct test_slab) and aligned to the alignment of test slab. If it fails then we panic. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-04-30[BLOCK] Don't pin lots of memory in mempoolsJens Axboe
Currently we scale the mempool sizes depending on memory installed in the machine, except for the bio pool itself which sits at a fixed 256 entry pre-allocation. There's really no point in "optimizing" this OOM path, we just need enough preallocated to make progress. A single unit is enough, lets scale it down to 2 just to be on the safe side. This patch saves ~150kb of pinned kernel memory on a 32-bit box. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2006-12-13[PATCH] optimize o_direct on block devicesChen, Kenneth W
Implement block device specific .direct_IO method instead of going through generic direct_io_worker for block device. direct_io_worker() is fairly complex because it needs to handle O_DIRECT on file system, where it needs to perform block allocation, hole detection, extents file on write, and tons of other corner cases. The end result is that it takes tons of CPU time to submit an I/O. For block device, the block allocation is much simpler and a tight triple loop can be written to iterate each iovec and each page within the iovec in order to construct/prepare bio structure and then subsequently submit it to the block layer. This significantly speeds up O_D on block device. [akpm@osdl.org: small speedup] Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Zach Brown <zach.brown@oracle.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-07[PATCH] slab: remove kmem_cache_tChristoph Lameter
Replace all uses of kmem_cache_t with struct kmem_cache. The patch was generated using the following script: #!/bin/sh # # Replace one string by another in all the kernel sources. # set -e for file in `find * -name "*.c" -o -name "*.h"|xargs grep -l $1`; do quilt add $file sed -e "1,\$s/$1/$2/g" $file >/tmp/$$ mv /tmp/$$ $file quilt refresh done The script was run like this sh replace kmem_cache_t "struct kmem_cache" Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-05Merge branch 'master' of ↵David Howells
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 Conflicts: drivers/infiniband/core/iwcm.c drivers/net/chelsio/cxgb2.c drivers/net/wireless/bcm43xx/bcm43xx_main.c drivers/net/wireless/prism54/islpci_eth.c drivers/usb/core/hub.h drivers/usb/input/hid-core.c net/core/netpoll.c Fix up merge failures with Linus's head and fix new compilation failures. Signed-Off-By: David Howells <dhowells@redhat.com>
2006-12-01[PATCH] block: support larger block pc requestsMike Christie
This patch modifies blk_rq_map/unmap_user() and the cdrom and scsi_ioctl.c users so that it supports requests larger than bio by chaining them together. Signed-off-by: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2006-12-01[PATCH] block: kill length alignment test in bio_map_user()Mike Christie
The target mode support is mapping in bios using bio_map_user. The current targets do not need their len to be aligned with a queue limit so this check is causing some problems. Note: pointers passed into the kernel are properly aligned by usersapace tgt code so the uaddr check in bio_map_user is ok. The major user, blk_bio_map_user checks for the len before mapping so it is not affected by this patch. And the semi-newly added user blk_rq_map_user_iov has been failing out when the len is not aligned properly so maybe people have been good and not sending misaligned lens or that path is not used very often and this change will not be very dangerous. st and sg do not check the length and we have not seen any problem reports from those wider used paths so this patch should be fairly safe - for mm and wider testing at least. Signed-off-by: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2006-11-22WorkStruct: Pass the work_struct pointer instead of context dataDavid Howells
Pass the work_struct pointer to the work function rather than context data. The work function can use container_of() to work out the data. For the cases where the container of the work_struct may go away the moment the pending bit is cleared, it is made possible to defer the release of the structure by deferring the clearing of the pending bit. To make this work, an extra flag is introduced into the management side of the work_struct. This governs auto-release of the structure upon execution. Ordinarily, the work queue executor would release the work_struct for further scheduling or deallocation by clearing the pending bit prior to jumping to the work function. This means that, unless the driver makes some guarantee itself that the work_struct won't go away, the work function may not access anything else in the work_struct or its container lest they be deallocated.. This is a problem if the auxiliary data is taken away (as done by the last patch). However, if the pending bit is *not* cleared before jumping to the work function, then the work function *may* access the work_struct and its container with no problems. But then the work function must itself release the work_struct by calling work_release(). In most cases, automatic release is fine, so this is the default. Special initiators exist for the non-auto-release case (ending in _NAR). Signed-Off-By: David Howells <dhowells@redhat.com>
2006-10-11[PATCH] fs/bio.c: tweaksAndreas Mohr
- Calculate a variable in bvec_alloc_bs() only once needed, not earlier (bio.o down from 18408 to 18376 Bytes, 32 Bytes saved, probably due to data locality improvements). - Init variable idx to silence a gcc warning which already existed in the unmodified original base file (bvec_alloc_bs() handles idx correctly, so there's no need for the warning): fs/bio.c: In function `bio_alloc_bioset': fs/bio.c:169: warning: `idx' may be used uninitialized in this function Signed-off-by: Andreas Mohr <andi@lisas.de> Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-30[PATCH] Update axboe@suse.de email addressJens Axboe
As people often look for the copyright in files to see who to mail, update the link to a neutral one. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-30[PATCH] fix creating zero sized bio mempools in low memory systemMilan Broz
In the very low memory systems is in the init_bio call scale parameter set to zero and it leads to creating zero sized mempool. This patch prevents pool_entries parameter become zero, so the created pool have at least 1 entry. Mempool with 0 entries lead to incorrect behaviour of mempool_free. (Alloc requests are not waken up and system stalls in mempool_alloc->ioschedule). Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-06-17[PATCH] Fix missing ret assignment in __bio_map_user() error pathJens Axboe
If get_user_pages() returns less pages than what we asked for, we jump to out_unmap which will return ERR_PTR(ret). But ret can contain a positive number just smaller than local_nr_pages, so be sure to set it to -EFAULT always. Problem found and diagnosed by Damien Le Moal <damien@sdl.hitachi.co.jp> Signed-off-by: Jens Axboe <axboe@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-05-23[PATCH] md: Make sure bi_max_vecs is set properly in bio_splitNeilBrown
Else a subsequent bio_clone might make a mess. Signed-off-by: Neil Brown <neilb@suse.de> Cc: "Don Dupuis" <dondster@gmail.com> Acked-by: Jens Axboe <axboe@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-26[PATCH] mempool: use mempool_create_slab_pool()Matthew Dobson
Modify well over a dozen mempool users to call mempool_create_slab_pool() rather than calling mempool_create() with extra arguments, saving about 30 lines of code and increasing readability. Signed-off-by: Matthew Dobson <colpatch@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-26[PATCH] mempool: use common mempool kmalloc allocatorMatthew Dobson
This patch changes several mempool users, all of which are basically just wrappers around kmalloc(), to use the common mempool_kmalloc/kfree, rather than their own wrapper function, removing a bunch of duplicated code. Signed-off-by: Matthew Dobson <colpatch@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-26[PATCH] Use __read_mostly on some hot fs variablesEric Dumazet
I discovered on oprofile hunting on a SMP platform that dentry lookups were slowed down because d_hash_mask, d_hash_shift and dentry_hashtable were in a cache line that contained inodes_stat. So each time inodes_stats is changed by a cpu, other cpus have to refill their cache line. This patch moves some variables to the __read_mostly section, in order to avoid false sharing. RCU dentry lookups can go full speed. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] use kzalloc and kcalloc in core fs codeOliver Neukum
Signed-off-by: Oliver Neukum <oliver@neukum.name> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-23[PATCH] Block queue IO tracing support (blktrace) as of 2006-03-23Jens Axboe
Signed-off-by: Jens Axboe <axboe@suse.de>
2006-03-23[PATCH] reduce size of bio mempoolsBenjamin LaHaise
The biovec default mempool limit of 256 entries results in over 3MB of RAM being permanently pinned, even on systems with only 128MB of RAM. Since mempool tries to allocate from the system pool first, it makes sense to reduce the size of the mempool fallbacks to a more reasonable limit of 1-5 entries -- enough for the system to be able to make progress even under load. Signed-off-by: Benjamin LaHaise <bcrl@kvack.org> Acked-by: Jens Axboe <axboe@suse.de> Cc: Matt Mackall <mpm@selenic.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-31[BLOCK] A few kerneldoc fixupsJens Axboe
Signed-off-by: Jens Axboe <axboe@suse.de>
2006-01-14[PATCH] Unlinline a bunch of other functionsArjan van de Ven
Remove the "inline" keyword from a bunch of big functions in the kernel with the goal of shrinking it by 30kb to 40kb Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Acked-by: Jeff Garzik <jgarzik@pobox.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-09[BLOCK] bio: init ->bi_bdev in bio_init()Jens Axboe
For SG_IO requests, bio->bi_bdev may not be explicitly initialized. So make bio_init() clear the field to make sure it's always NULL or valid. Signed-off-by: Jens Axboe <axboe@suse.de>
2006-01-06[BLOCK] bio: check for same page merge possibilities in __bio_add_page()Jens Axboe
For filesystems with a blocksize < page size, we can merge same page calls into the bio_vec at the end of the bio. This saves segments on systems with a page size > the "normal" 4kb fs block size. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@suse.de>
2005-12-15[SCSI] seperate max_sectors from max_hw_sectorsMike Christie
- export __blk_put_request and blk_execute_rq_nowait needed for async REQ_BLOCK_PC requests - seperate max_hw_sectors and max_sectors for block/scsi_ioctl.c and SG_IO bio.c helpers per Jens's last comments. Since block/scsi_ioctl.c SG_IO was already testing against max_sectors and SCSI-ml was setting max_sectors and max_hw_sectors to the same value this does not change any scsi SG_IO behavior. It only prepares ll_rw_blk.c, scsi_ioctl.c and bio.c for when SCSI-ml begins to set a valid max_hw_sectors for all LLDs. Today if a LLD does not set it SCSI-ml sets it to a safe default and some LLDs set it to a artificial low value to overcome memory and feedback issues. Note: Since we now cap max_sectors to BLK_DEF_MAX_SECTORS, which is 1024, drivers that used to call blk_queue_max_sectors with a large value of max_sectors will now see the fs requests capped to BLK_DEF_MAX_SECTORS. Signed-off-by: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
2005-12-14[SCSI] Convert SCSI mid-layer to scsi_execute_asyncMike Christie
Add scsi helpers to create really-large-requests and convert scsi-ml to scsi_execute_async(). Per Jens's previous comments, I placed this function in scsi_lib.c. I made it follow all the queue's limits - I think I did at least :), so I removed the warning on the function header. I think the scsi_execute_* functions should eventually take a request_queue and be placed some place where the dm-multipath hw_handler can use them if that failover code is going to stay in the kernel. That conversion patch will be sent in another mail though. Signed-off-by: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
2005-10-28[PATCH] gfp_t: fs/*Al Viro
- ->releasepage() annotated (s/int/gfp_t), instances updated - missing gfp_t in fs/* added - fixed misannotation from the original sweep caught by bitwise checks: XFS used __nocast both for gfp_t and for flags used by XFS allocator. The latter left with unsigned int __nocast; we might want to add a different type for those but for now let's leave them alone. That, BTW, is a case when __nocast use had been actively confusing - it had been used in the same code for two different and similar types, with no way to catch misuses. Switch of gfp_t to bitwise had caught that immediately... One tricky bit is left alone to be dealt with later - mapping->flags is a mix of gfp_t and error indications. Left alone for now. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-08[PATCH] gfp flags annotations - part 1Al Viro
- added typedef unsigned int __nocast gfp_t; - replaced __nocast uses for gfp flags with gfp_t - it gives exactly the same warnings as far as sparse is concerned, doesn't change generated code (from gcc point of view we replaced unsigned int with typedef) and documents what's going on far better. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-09[PATCH] bogus cast in bio.cviro@ZenIV.linux.org.uk
<qualifier> void * is not the same as void <qualifier> *... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-07Merge master.kernel.org:/pub/scm/linux/kernel/git/jejb/scsi-for-linus-2.6 Linus Torvalds
2005-09-07[PATCH] kill bio->bi_setPeter Osterlund
Jens: ->bi_set is totally unnecessary bloat of struct bio. Just define a proper destructor for the bio and it already knows what bio_set it belongs too. Peter: Fixed the bugs. Signed-off-by: Jens Axboe <axboe@suse.de> Signed-off-by: Peter Osterlund <petero2@telia.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-08-28fix mismerge in ll_rw_blk.cJames Bottomley
2005-08-07[PATCH] __bio_clone() dead commentAndrew Morton
Remove a very wrong comment. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-07-28[PATCH] bio_clone fixAndrew Morton
Fix bug introduced in 2.6.11-rc2: when we clone a BIO we need to copy over the current index into it as well. It corrupts data with some MD setups. See http://bugzilla.kernel.org/show_bug.cgi?id=4946 Huuuuuuuuge thanks to Matthew Stapleton <matthew4196@gmail.com> for doggedly chasing this one down. Acked-by: Jens Axboe <axboe@suse.de> Cc: <linux-raid@vger.kernel.org> Cc: <dm-devel@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-07-07[PATCH] mostly_read data sectionChristoph Lameter
Add a new section called ".data.read_mostly" for data items that are read frequently and rarely written to like cpumaps etc. If these maps are placed in the .data section then these frequenly read items may end up in cachelines with data is is frequently updated. In that case all processors in an SMP system must needlessly reload the cachelines again and again containing elements of those frequently used variables. The ability to share these cachelines will allow each cpu in an SMP system to keep local copies of those shared cachelines thereby optimizing performance. Signed-off-by: Alok N Kataria <alokk@calsoftinc.com> Signed-off-by: Shobhit Dayal <shobhit@calsoftinc.com> Signed-off-by: Christoph Lameter <christoph@scalex86.org> Signed-off-by: Shai Fultheim <shai@scalex86.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>