linux-raid.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: NeilBrown <neilb@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
	Dan Williams <dan.j.williams@intel.com>
Subject: [PATCH 019 of 29] md: md: kill STRIPE_OP_MOD_DMA in raid5 offload
Date: Fri, 27 Jun 2008 16:51:23 +1000	[thread overview]
Message-ID: <1080627065123.10617@suse.de> (raw)
In-Reply-To: 20080627164503.9671.patches@notabene


From: Dan Williams <dan.j.williams@intel.com>

This micro-optimization allowed the raid code to skip a re-read of the
parity block after checking parity.  It took advantage of the fact that
xor-offload-engines have their own internal result buffer and can check
parity without writing to memory.  Remove it for the following reasons:

1/ It is a layering violation for MD to need to manage the DMA and
   non-DMA paths within async_xor_zero_sum
2/ Bad precedent to toggle the 'ops' flags outside the lock
3/ Hard to realize a performance gain as reads will not need an updated
   parity block and writes will dirty it anyways.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./drivers/md/raid5.c         |   10 ----------
 ./include/linux/raid/raid5.h |    2 --
 2 files changed, 12 deletions(-)

diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c
--- .prev/drivers/md/raid5.c	2008-06-27 16:20:58.000000000 +1000
+++ ./drivers/md/raid5.c	2008-06-27 16:22:03.000000000 +1000
@@ -837,15 +837,10 @@ ops_run_postxor(struct stripe_head *sh, 
 static void ops_complete_check(void *stripe_head_ref)
 {
 	struct stripe_head *sh = stripe_head_ref;
-	int pd_idx = sh->pd_idx;
 
 	pr_debug("%s: stripe %llu\n", __func__,
 		(unsigned long long)sh->sector);
 
-	if (test_and_clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending) &&
-		sh->ops.zero_sum_result == 0)
-		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-
 	set_bit(STRIPE_OP_CHECK, &sh->ops.complete);
 	set_bit(STRIPE_HANDLE, &sh->state);
 	release_stripe(sh);
@@ -873,11 +868,6 @@ static void ops_run_check(struct stripe_
 	tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
 		&sh->ops.zero_sum_result, 0, NULL, NULL, NULL);
 
-	if (tx)
-		set_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
-	else
-		clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
-
 	atomic_inc(&sh->count);
 	tx = async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
 		ops_complete_check, sh);

diff .prev/include/linux/raid/raid5.h ./include/linux/raid/raid5.h
--- .prev/include/linux/raid/raid5.h	2008-06-27 16:20:33.000000000 +1000
+++ ./include/linux/raid/raid5.h	2008-06-27 16:22:03.000000000 +1000
@@ -267,10 +267,8 @@ struct r6_state {
 
 /* modifiers to the base operations
  * STRIPE_OP_MOD_REPAIR_PD - compute the parity block and write it back
- * STRIPE_OP_MOD_DMA_CHECK - parity is not corrupted by the check
  */
 #define STRIPE_OP_MOD_REPAIR_PD 7
-#define STRIPE_OP_MOD_DMA_CHECK 8
 
 /*
  * Plugging:

  parent reply	other threads:[~2008-06-27  6:51 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-06-27  6:49 [PATCH 000 of 29] md: Introduction : patchbomb for 2.6.27 merge window NeilBrown
2008-06-27  6:49 ` [PATCH 001 of 29] md: Ensure interrupted recovery completed properly (v1 metadata plus bitmap) NeilBrown
2008-07-01  7:20   ` Jan Engelhardt
2008-06-27  6:49 ` [PATCH 002 of 29] md: Don't acknowlege that stripe-expand is complete until it really is NeilBrown
2008-06-27  6:49 ` [PATCH 003 of 29] md: Fix error paths if md_probe fails NeilBrown
2008-06-27  6:49 ` [PATCH 004 of 29] md: linear: correct disk numbering error check NeilBrown
2008-06-27  6:49 ` [PATCH 005 of 29] md: use bio_endio instead of a call to bi_end_io NeilBrown
2008-06-27  6:49 ` [PATCH 006 of 29] md: Improve setting of "events_cleared" for write-intent bitmaps NeilBrown
2008-06-27  6:50 ` [PATCH 007 of 29] md: Allow setting start point for requested check/repair NeilBrown
2008-06-27  6:50 ` [PATCH 008 of 29] md: Close race in md_probe NeilBrown
2008-06-27 12:21   ` Andre Noll
2008-06-27 23:38     ` Neil Brown
2008-06-30  7:52       ` Andre Noll
2008-06-27  6:50 ` [PATCH 009 of 29] md: Don't try to make md arrays dirty if that is not meaningful NeilBrown
2008-06-27  6:50 ` [PATCH 010 of 29] md: Enable setting of 'offset' and 'size' of a hot-added spare NeilBrown
2008-06-27  6:50 ` [PATCH 011 of 29] md: Support adding a spare to a live md array with external metadata NeilBrown
2008-06-27  6:50 ` [PATCH 012 of 29] md: rationalise return value for ->hot_add_disk method NeilBrown
2008-06-27  6:50 ` [PATCH 013 of 29] md: Don't reject HOT_REMOVE_DISK request for an array that is not yet started NeilBrown
2008-06-27  6:50 ` [PATCH 014 of 29] md: Make sure all changes to md/array_state are notified NeilBrown
2008-06-27  6:50 ` [PATCH 015 of 29] md: Make sure all changes to md/sync_action " NeilBrown
2008-06-27  6:51 ` [PATCH 016 of 29] md: Make sure all changes to md/degraded " NeilBrown
2008-06-27  6:51 ` [PATCH 017 of 29] md: Make sure all changes to md/dev-XX/state " NeilBrown
2008-06-27  6:51 ` [PATCH 018 of 29] md: Support changing rdev size on running arrays NeilBrown
2008-06-27 16:09   ` Markus Hochholdinger
2008-06-27 23:41     ` Neil Brown
2010-03-30 14:52       ` Markus Hochholdinger
2010-03-31  5:41         ` Neil Brown
2010-04-01 15:23           ` Markus Hochholdinger
2012-03-24 20:47       ` Markus Hochholdinger
2012-03-25 22:15         ` NeilBrown
2021-11-10 13:09         ` Markus Hochholdinger
2021-11-10 17:51           ` Markus Hochholdinger
2021-11-11 13:10             ` Markus Hochholdinger
2021-11-11 15:09               ` Markus Hochholdinger
2021-11-12  1:22                 ` Guoqing Jiang
2021-11-12 14:31                   ` Markus Hochholdinger
2008-06-27  6:51 ` NeilBrown [this message]
2008-06-27  6:51 ` [PATCH 020 of 29] md: md: kill STRIPE_OP_IO flag NeilBrown
2008-06-27  6:51 ` [PATCH 021 of 29] md: md: use stripe_head_state in ops_run_io() NeilBrown
2008-06-27  6:51 ` [PATCH 022 of 29] md: md: unify raid5/6 i/o submission NeilBrown
2008-06-27  6:51 ` [PATCH 023 of 29] md: md: replace STRIPE_OP_CHECK with 'check_states' NeilBrown
2008-06-27  6:51 ` [PATCH 024 of 29] md: md: replace STRIPE_OP_BIOFILL with STRIPE_BIOFILL_RUN NeilBrown
2008-06-27  6:52 ` [PATCH 025 of 29] md: md: replace STRIPE_OP_COMPUTE_BLK with STRIPE_COMPUTE_RUN NeilBrown
2008-06-27  6:52 ` [PATCH 026 of 29] md: md: replace STRIPE_OP_{BIODRAIN,PREXOR,POSTXOR} with 'reconstruct_states' NeilBrown
2008-06-27  6:52 ` [PATCH 027 of 29] md: md: replace R5_WantPrexor with R5_WantDrain, add 'prexor' reconstruct_states NeilBrown
2008-06-27  6:52 ` [PATCH 028 of 29] md: md: handle operation chaining in raid5_run_ops NeilBrown
2008-06-27  6:52 ` [PATCH 029 of 29] md: md: rationalize raid5 function names NeilBrown

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1080627065123.10617@suse.de \
    --to=neilb@suse.de \
    --cc=akpm@linux-foundation.org \
    --cc=dan.j.williams@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-raid@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).