The patch titled ipc/sem.c: sem optimise undo list search has been added to the -mm tree. Its filename is ipc-semc-sem-optimise-undo-list-search.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: ipc/sem.c: sem optimise undo list search From: Nick Piggin <npiggin@xxxxxxx> Around a month ago, there was some discussion about an improvement of the sysv sem algorithm: Most (at least: some important) users only use simple semaphore operations, therefore it's worthwile to optimize this use case. This patch: Move last looked up sem_undo struct to the head of the task's undo list. Attempt to move common entries to the front of the list so search time is reduced. This reduces lookup_undo on oprofile of problematic SAP workload by 30% (see patch 4 for a description of SAP workload). Signed-off-by: Nick Piggin <npiggin@xxxxxxx> Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> Cc: Pierre Peiffer <peifferp@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- ipc/sem.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) diff -puN ipc/sem.c~ipc-semc-sem-optimise-undo-list-search ipc/sem.c --- a/ipc/sem.c~ipc-semc-sem-optimise-undo-list-search +++ a/ipc/sem.c @@ -961,17 +961,31 @@ static inline int get_undo_list(struct s return 0; } -static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) +static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) { - struct sem_undo *walk; + struct sem_undo *un; - list_for_each_entry_rcu(walk, &ulp->list_proc, list_proc) { - if (walk->semid == semid) - return walk; + list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) { + if (un->semid == semid) + return un; } return NULL; } +static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) +{ + struct sem_undo *un; + + assert_spin_locked(&ulp->lock); + + un = __lookup_undo(ulp, semid); + if (un) { + list_del_rcu(&un->list_proc); + list_add_rcu(&un->list_proc, &ulp->list_proc); + } + return un; +} + /** * find_alloc_undo - Lookup (and if not present create) undo array * @ns: namespace @@ -1307,7 +1321,7 @@ void exit_sem(struct task_struct *tsk) if (IS_ERR(sma)) continue; - un = lookup_undo(ulp, semid); + un = __lookup_undo(ulp, semid); if (un == NULL) { /* exit_sem raced with IPC_RMID+semget() that created * exactly the same semid. Nothing to do. _ Patches currently in -mm which might be from npiggin@xxxxxxx are linux-next.patch fs-remove-unneeded-dcache_unhashed-tricks.patch fs-improve-remountro-vs-buffercache-coherency.patch ipc-semc-sem-optimise-undo-list-search.patch ipc-semc-sem-use-list-operations.patch ipc-semc-sem-preempt-improve.patch ipc-semc-optimize-if-semops-fail.patch ipc-semc-add-a-per-semaphore-pending-list.patch ipc-semc-optimize-single-semop-operations.patch ipc-semc-optimize-single-sops-when-semval-is-zero.patch reiser4.patch fs-symlink-write_begin-allocation-context-fix-reiser4-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html