On Tue, 10 May 2011, Amir G. wrote: > On Tue, May 10, 2011 at 4:48 PM, Lukas Czerner <lczerner@xxxxxxxxxx> wrote: > > On Thu, 24 Mar 2011, amir73il@xxxxxxxxxxxxxxxxxxxxx wrote: > > > >> The purpose of this patch set is the removal of grp->alloc_sem locks > >> from block allocation paths. > >> > >> The resulting code is cleaner and should perform better in concurrent > >> allocating tasks workloads. > > Hi Amir, > > > > Do you have any performance numbers indicating performance improvement > > in concurrent allocations ? The only point where I can see taking > > write semaphore is in filesystem resize code. Or am I missing something ? > > Yes, you are. down_write is also taken when initializing a block group > buddy cache for the first time (NEED_INIT flag is set). > Anyway, I do NOT have any performance number since this wasn't the purpose of > this work. This work was done for snapshots, but I do think that as I wrote: > 1. The resulting code is cleaner > 2. Getting rid of an unneeded semaphore in allocation path can only do good > to performance, but I certainly don't have the kind of high scalability testing > setup to show the performance improvements if there are any. Well everyone who wants to use that group has to wait for this initialization anyway, right ? Of course I know that the purpose of this was to ease your snapshot work, but I do not see that stated anywhere in the description ;). Anyway I was just curious what impact does this have on the performance since you've mentioned that, if you do not have any I am ok with that. Btw, patches looks good to me, but I have not done _very_ deep review. Thanks! -Lukas > > > > > Thanks! > > -Lukas > > > >> > >> I ran several xfstests runs with these patches (4K and 1K block size). > >> I tried several online resizes and verifyed that both in-core and on-disk > >> group counters are correct. > >> > >> v2->v1: > >> - fix silly bug in patch 4/5 that triggers BUG_ON(incore == NULL) > >> - replace get_undo_access() with get_write_access() > >> - ran xfstests with block size 1K (where 2 groups share a buddy page) > >> > >> [PATCH v2 1/5] ext4: move ext4_add_groupblocks() to mballoc.c > >> [PATCH v2 2/5] ext4: implement ext4_add_groupblocks() by freeing blocks > >> [PATCH v2 3/5] ext4: synchronize ext4_mb_init_group() with buddy page lock > >> [PATCH v2 4/5] ext4: teach ext4_mb_init_cache() to skip uptodate buddy caches > >> [PATCH v2 5/5] ext4: remove alloc_semp > >> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > >> the body of a message to majordomo@xxxxxxxxxxxxxxx > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >> > > > > -- > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html >
