From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukas Straub Subject: Re: [PATCH v2] dm-integrity: Prevent RMW for full metadata buffer writes Date: Thu, 26 Mar 2020 12:24:18 +0100 Message-ID: <20200326122418.741b2ffc@luklap> References: <20200227142601.61f3cd54@luklap> <20200324171821.GA2444@redhat.com> <20200324195912.518dc87c@luklap> <20200324191148.GA2921@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="Sig_/rBuFSl4aDuDI2ufSEpF2qcj"; protocol="application/pgp-signature"; micalg=pgp-sha512 Return-path: In-Reply-To: <20200324191148.GA2921@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Mike Snitzer Cc: linux-kernel , Alasdair Kergon , dm-devel , Mikulas Patocka List-Id: dm-devel.ids --Sig_/rBuFSl4aDuDI2ufSEpF2qcj Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 24 Mar 2020 15:11:49 -0400 Mike Snitzer wrote: > On Tue, Mar 24 2020 at 2:59pm -0400, > Lukas Straub wrote: >=20 > > On Tue, 24 Mar 2020 13:18:22 -0400 > > Mike Snitzer wrote: > > =20 > > > On Thu, Feb 27 2020 at 8:26am -0500, > > > Lukas Straub wrote: > > > =20 > > > > If a full metadata buffer is being written, don't read it first. Th= is > > > > prevents a read-modify-write cycle and increases performance on HDDs > > > > considerably. > > > >=20 > > > > To do this we now calculate the checksums for all sectors in the bi= o in one > > > > go in integrity_metadata and then pass the result to dm_integrity_r= w_tag, > > > > which now checks if we overwrite the whole buffer. > > > >=20 > > > > Benchmarking with a 5400RPM HDD with bitmap mode: > > > > integritysetup format --no-wipe --batch-mode --interleave-sectors $= ((64*1024)) -t 4 -s 512 -I crc32c -B /dev/sdc > > > > integritysetup open --buffer-sectors=3D1 -I crc32c -B /dev/sdc hdda= _integ > > > > dd if=3D/dev/zero of=3D/dev/mapper/hdda_integ bs=3D64K count=3D$((1= 6*1024*4)) conv=3Dfsync oflag=3Ddirect status=3Dprogress > > > >=20 > > > > Without patch: > > > > 4294967296 bytes (4.3 GB, 4.0 GiB) copied, 400.326 s, 10.7 MB/s > > > >=20 > > > > With patch: > > > > 4294967296 bytes (4.3 GB, 4.0 GiB) copied, 41.2057 s, 104 MB/s > > > >=20 > > > > Signed-off-by: Lukas Straub > > > > --- > > > > Hello Everyone, > > > > So here is v2, now checking if we overwrite a whole metadata buffer= instead > > > > of the (buggy) check if we overwrite a whole tag area before. > > > > Performance stayed the same (with --buffer-sectors=3D1). > > > >=20 > > > > The only quirk now is that it advertises a very big optimal io size= in the > > > > standard configuration (where buffer_sectors=3D128). Is this a Prob= lem? > > > >=20 > > > > v2: > > > > -fix dm_integrity_rw_tag to check if we overwrite a whole metadat = buffer > > > > -fix optimal io size to check if we overwrite a whole metadata buf= fer > > > >=20 > > > > Regards, > > > > Lukas Straub =20 > > >=20 > > >=20 > > > Not sure why you didn't cc Mikulas but I just checked with him and he > > > thinks: > > >=20 > > > You're only seeing a boost because you're using 512-byte sector and > > > 512-byte buffer. Patch helps that case but hurts in most other cases > > > (due to small buffers). =20 > >=20 > > Hmm, buffer-sectors is still user configurable. If the user wants fast > > write performance on slow HDDs he can set a small buffer-sector and > > benefit from this patch. With the default buffer-sectors=3D128 it > > shouldn't have any impact. =20 >=20 > OK, if you'd be willing to conduct tests to prove there is no impact > with larger buffers that'd certainly help reinforce your position and > make it easier for me to take your patch. >=20 > But if you're just testing against slow HDD testbeds then the test > coverage isn't wide enough. >=20 > Thanks, > Mike >=20 Sure, This time testing with an Samsung 850 EVO SSD: without patch: root@teststore:/home/lukas# integritysetup format --no-wipe --batch-mode -I= crc32c -B /dev/sdc1 root@teststore:/home/lukas# integritysetup open -I crc32c -B /dev/sdc1 ssda= _integ root@teststore:/home/lukas# dd if=3D/dev/zero of=3D/dev/mapper/ssda_integ b= s=3D64K count=3D$((16*1024*4)) conv=3Dfsync oflag=3Ddirect status=3Dprogress 4177264640 bytes (4.2 GB, 3.9 GiB) copied, 28 s, 149 MB/s 65536+0 records in 65536+0 records out 4294967296 bytes (4.3 GB, 4.0 GiB) copied, 28.8946 s, 149 MB/s root@teststore:/home/lukas# dd if=3D/dev/zero of=3D/dev/mapper/ssda_integ b= s=3D4M count=3D$((256*4)) conv=3Dfsync oflag=3Ddirect status=3Dprogress 4211081216 bytes (4.2 GB, 3.9 GiB) copied, 22 s, 191 MB/s 1024+0 records in 1024+0 records out 4294967296 bytes (4.3 GB, 4.0 GiB) copied, 22.6355 s, 190 MB/s root@teststore:/home/lukas# time mkfs.ext4 /dev/mapper/ssda_integ 4g mke2fs 1.45.5 (07-Jan-2020) Creating filesystem with 1048576 4k blocks and 262144 inodes Filesystem UUID: 679c4808-d549-4576-a8ef-4c46c78c6070 Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736 Allocating group tables: done Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: done real 0m0.318s user 0m0.016s sys 0m0.001s root@teststore:/home/lukas# mount /dev/mapper/ssda_integ /mnt/ root@teststore:/home/lukas# cd /mnt/ root@teststore:/mnt# time tar -xJf /home/lukas/linux-5.5.4.tar.xz real 0m18.708s user 0m14.351s sys 0m8.585s root@teststore:/mnt# time rm -rf linux-5.5.4/ real 0m3.226s user 0m0.117s sys 0m2.958s with patch: root@teststore:/home/lukas# integritysetup format --no-wipe --batch-mode -I= crc32c -B /dev/sdc1 root@teststore:/home/lukas# integritysetup open -I crc32c -B /dev/sdc1 ssda= _integ root@teststore:/home/lukas# dd if=3D/dev/zero of=3D/dev/mapper/ssda_integ b= s=3D64K count=3D$((16*1024*4)) conv=3Dfsync oflag=3Ddirect status=3Dprogress 4169007104 bytes (4.2 GB, 3.9 GiB) copied, 27 s, 154 MB/s 65536+0 records in 65536+0 records out 4294967296 bytes (4.3 GB, 4.0 GiB) copied, 27.9165 s, 154 MB/s root@teststore:/home/lukas# dd if=3D/dev/zero of=3D/dev/mapper/ssda_integ b= s=3D4M count=3D$((256*4)) conv=3Dfsync oflag=3Ddirect status=3Dprogress 4169138176 bytes (4.2 GB, 3.9 GiB) copied, 22 s, 189 MB/s 1024+0 records in 1024+0 records out 4294967296 bytes (4.3 GB, 4.0 GiB) copied, 22.9181 s, 187 MB/s root@teststore:/home/lukas# time mkfs.ext4 /dev/mapper/ssda_integ 4g mke2fs 1.45.5 (07-Jan-2020) Creating filesystem with 1048576 4k blocks and 262144 inodes Filesystem UUID: 9a9decad-19e2-46a4-8cc5-ce27238829f2 Superblock backups stored on blocks:=20 32768, 98304, 163840, 229376, 294912, 819200, 884736 Allocating group tables: done =20 Writing inode tables: done =20 Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: done=20 real 0m0.341s user 0m0.000s sys 0m0.016s root@teststore:/home/lukas# mount /dev/mapper/ssda_integ /mnt/ root@teststore:/home/lukas# cd /mnt/ root@teststore:/mnt# time tar -xJf /home/lukas/linux-5.5.4.tar.xz real 0m18.409s user 0m14.191s sys 0m8.585s root@teststore:/mnt# time rm -rf linux-5.5.4/ real 0m3.200s user 0m0.133s sys 0m2.979s Regards, Lukas Straub --Sig_/rBuFSl4aDuDI2ufSEpF2qcj Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEg/qxWKDZuPtyYo+kNasLKJxdslgFAl58kOIACgkQNasLKJxd sljn2Q//fdRtqln3arcfUfX72NS0AlgI0CCCB7uwcn974EK4BeqEKJeu612dloWE I9CXr6d47xbsJ0V3rsiPyLilbFWLc4898optf0PqEvI8rQ4ksbY9lEuS0vqkymSR GeIMEQNbpn5uK+K+zVDGnR5Yg1+XYsfxTwGtwotHmFGMfYBYnCIClEc2gPykMW+Z 9hfaCdpLYAy51yHqawZsIjz7wdPfp5EQB2Mcs4nl4vV9rp24T+Vs8qOaA2E1c1OE hGpSX9b+Gs0UW5pT6DJyScugqIdkSEvKwGyz1riisrLHnUP3M9akDlVcMUU/Q8o3 xV9N473P7ZYUP3dqcHPUQoeTP4xhzWXM6cQHPVWNHfaTQz7c+gJP6duRw5kT2PVD 1AEuciRZcSqvz6dXoYoY2pCQ/nh7Ry4T2yqi/rVQhity10ZJRKYXWYviwnRP+Kxg wPfONRya5iMHBKHspO6eVpkS2B6jPd4UHhiDFnj1/Ls66ijo3G4VccdNl0OWpjv6 tSTP3Cl2BrC9NjwzerhFSmU+7K5WReOWeah0eOeiBRV5BDrZ4x8FZA6QqhHjBKlQ 7TXyhRf7KcK06rgB3tRUtG3/P7kQx3KY8H4sLOtlngYgqBYmAstXBa0BG7Md51v0 qI5Y2smMmHI/UBnaPw+xZZTxqHBF4A/jAJLAZZs5krKUuiSTdNQ= =pSN3 -----END PGP SIGNATURE----- --Sig_/rBuFSl4aDuDI2ufSEpF2qcj--