Just wondering if this patch is adequate or there's more to come. I want to put a fix into our 2.6.32 kernel. Thanks. > -----Original Message----- > From: linux-ext4-owner@xxxxxxxxxxxxxxx > [mailto:linux-ext4-owner@xxxxxxxxxxxxxxx] On Behalf Of Eric Sandeen > Sent: Monday, August 30, 2010 10:06 PM > To: Bill Fink > Cc: tytso@xxxxxxx; adilger@xxxxxxx; > linux-ext4@xxxxxxxxxxxxxxx; bill.fink@xxxxxxxx > Subject: Re: [PATCH] ext4: fix 50% disk write performance regression > > Bill Fink wrote: > > On Mon, 30 Aug 2010, Eric Sandeen wrote: > > > >> Can you give this a shot? > >> > >> The first hunk is, I think, the biggest problem. Even if > >> we get the max number of pages we need, we keep scanning forward > >> until "done" without doing any more actual, useful work. > >> > >> The 2nd hunk is an oddity, some places assign nr_to_write > >> to LONG_MAX, and we get here and multiply -that- by 8... giving > >> us "-8" for nr_to_write, that can't help things when we > >> do later comparisons on that number... > >> > >> I also see us asking to find pages starting at "idx" and > >> the first dirty page we find is well ahead of that, > >> I'm not sure if that's indicative of a problem or not. > >> > >> Anyway, want to give this a shot, in place of the patch you sent, > >> and see how it fares compared to stock and/or with your patch? > >> > >> It's build-and-sanity tested but not really performance > tested here. > >> > >> Thanks, > >> -Eric > > > > Great! It looks like that does the trick. > > > > 2.6.35 + your patch: > > > > i7test7% dd if=/dev/zero of=/i7raid/bill/testfile1 bs=1M count=32768 > > 32768+0 records in > > 32768+0 records out > > 34359738368 bytes (34 GB) copied, 50.6702 s, 678 MB/s > > > > That's the same performance as with my patch, and pretty darn > > close to the original 2.6.31 performance. > > hah, that's good esp. considering my followup email that found > what I think is a problem with my patch. ;) > > What happens if you change: > > if (!range_cyclic && range_whole && wbc->nr_to_write != > LONG_MAX) > desired_nr_to_write = wbc->nr_to_write * 8; > else > desired_nr_to_write = ext4_num_dirty_pages(inode, index, > > to: > > if (!range_cyclic && range_whole) { > if (wbc->nr_to_write != LONG_MAX) > desired_nr_to_write = wbc->nr_to_write * 8; > else > desired_nr_to_write = wbc->nr_to_write; > } else > desired_nr_to_write = ext4_num_dirty_pages(inode, index, > > and see how that fares? I think that makes a little more sense, if we > got there with LONG_MAX that means "write everything" and > there's no need > to bump it up or to go counting pages. It may not make any > real difference. > > But I'm seeing really weird behavior in writeback, it starts > out nicely > writing 32768 pages at a time, and then goes all wonky, > revisiting pages > it's already done and doing IO in little chunks. This is > going to take > some staring I think. > > -Eric > > > > > -Thanks a bunch > > > > -Bill > > > > > > > >> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > >> index 4b8debe..33c2167 100644 > >> --- a/fs/ext4/inode.c > >> +++ b/fs/ext4/inode.c > >> @@ -1207,8 +1207,10 @@ static pgoff_t > ext4_num_dirty_pages(struct inode *inode, pgoff_t idx, > >> break; > >> idx++; > >> num++; > >> - if (num >= max_pages) > >> - break; > >> + if (num >= max_pages) { > >> + pagevec_release(&pvec); > >> + return num; > >> + } > >> } > >> pagevec_release(&pvec); > >> } > >> @@ -3002,7 +3004,7 @@ static int ext4_da_writepages(struct > address_space *mapping, > >> * sbi->max_writeback_mb_bump whichever is smaller. > >> */ > >> max_pages = sbi->s_max_writeback_mb_bump << (20 - > PAGE_CACHE_SHIFT); > : > > -- > 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
