Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=de08dbc1977419efa47eb71f10d96a98eb5bb111
Commit:     de08dbc1977419efa47eb71f10d96a98eb5bb111
Parent:     249a8c1124653fa90f3a3afff869095a31bc229f
Author:     David Chinner <[EMAIL PROTECTED]>
AuthorDate: Tue Feb 5 12:13:38 2008 +1100
Committer:  Lachlan McIlroy <[EMAIL PROTECTED]>
CommitDate: Thu Feb 7 18:23:05 2008 +1100

    [XFS] Make xfs_ail_check check less by default
    
    Checking the entire AIL on every insert and remove is prohibitively
    expensive - the sustained sequntial create rate on a single disk drops
    from about 1800/s to 60/s because of this checking resulting in the
    xfslogd becoming cpu bound.
    
    By default on debug builds, only check the next and previous entries in
    the list to ensure they are ordered correctly. If you really want, define
    XFS_TRANS_DEBUG to use the old behaviour.
    
    SGI-PV: 972759
    SGI-Modid: xfs-linux-melb:xfs-kern:30372a
    
    Signed-off-by: David Chinner <[EMAIL PROTECTED]>
    Signed-off-by: Lachlan McIlroy <[EMAIL PROTECTED]>
---
 fs/xfs/xfs_trans_ail.c |   37 ++++++++++++++++++++++++++++---------
 1 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 7ed7425..4d6330e 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -34,9 +34,9 @@ STATIC xfs_log_item_t * xfs_ail_min(xfs_ail_entry_t *);
 STATIC xfs_log_item_t * xfs_ail_next(xfs_ail_entry_t *, xfs_log_item_t *);
 
 #ifdef DEBUG
-STATIC void xfs_ail_check(xfs_ail_entry_t *);
+STATIC void xfs_ail_check(xfs_ail_entry_t *, xfs_log_item_t *);
 #else
-#define        xfs_ail_check(a)
+#define        xfs_ail_check(a,l)
 #endif /* DEBUG */
 
 
@@ -563,7 +563,7 @@ xfs_ail_insert(
        next_lip->li_ail.ail_forw = lip;
        lip->li_ail.ail_forw->li_ail.ail_back = lip;
 
-       xfs_ail_check(base);
+       xfs_ail_check(base, lip);
        return;
 }
 
@@ -577,12 +577,12 @@ xfs_ail_delete(
        xfs_log_item_t  *lip)
 /* ARGSUSED */
 {
+       xfs_ail_check(base, lip);
        lip->li_ail.ail_forw->li_ail.ail_back = lip->li_ail.ail_back;
        lip->li_ail.ail_back->li_ail.ail_forw = lip->li_ail.ail_forw;
        lip->li_ail.ail_forw = NULL;
        lip->li_ail.ail_back = NULL;
 
-       xfs_ail_check(base);
        return lip;
 }
 
@@ -626,13 +626,13 @@ xfs_ail_next(
  */
 STATIC void
 xfs_ail_check(
-       xfs_ail_entry_t *base)
+       xfs_ail_entry_t *base,
+       xfs_log_item_t  *lip)
 {
-       xfs_log_item_t  *lip;
        xfs_log_item_t  *prev_lip;
 
-       lip = base->ail_forw;
-       if (lip == (xfs_log_item_t*)base) {
+       prev_lip = base->ail_forw;
+       if (prev_lip == (xfs_log_item_t*)base) {
                /*
                 * Make sure the pointers are correct when the list
                 * is empty.
@@ -642,9 +642,27 @@ xfs_ail_check(
        }
 
        /*
+        * Check the next and previous entries are valid.
+        */
+       ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
+       prev_lip = lip->li_ail.ail_back;
+       if (prev_lip != (xfs_log_item_t*)base) {
+               ASSERT(prev_lip->li_ail.ail_forw == lip);
+               ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
+       }
+       prev_lip = lip->li_ail.ail_forw;
+       if (prev_lip != (xfs_log_item_t*)base) {
+               ASSERT(prev_lip->li_ail.ail_back == lip);
+               ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) >= 0);
+       }
+
+
+#ifdef XFS_TRANS_DEBUG
+       /*
         * Walk the list checking forward and backward pointers,
         * lsn ordering, and that every entry has the XFS_LI_IN_AIL
-        * flag set.
+        * flag set. This is really expensive, so only do it when
+        * specifically debugging the transaction subsystem.
         */
        prev_lip = (xfs_log_item_t*)base;
        while (lip != (xfs_log_item_t*)base) {
@@ -659,5 +677,6 @@ xfs_ail_check(
        }
        ASSERT(lip == (xfs_log_item_t*)base);
        ASSERT(base->ail_back == prev_lip);
+#endif /* XFS_TRANS_DEBUG */
 }
 #endif /* DEBUG */
-
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