Hi Boris, On Fri, Apr 20, 2018 at 07:19:24PM +0200, Boris Brezillon wrote: > On Fri, 20 Apr 2018 10:52:41 +0200 > Quentin Schulz <quentin.sch...@bootlin.com> wrote: > > > There's already ECC on NAND pages so there may be no need for one to > > check the CRC of a UBI volume. > > That's true that ECC can help detecting corruptions, but I don't think > this is the actual reason for disabling CRC check at volume open time. > The actual reason for doing that is when the UBI volume user (in our > case the squashfs FS) is also checking data consistency on its own > (which is the case for squashfs). > > > > > Let's introduce a ubi.nocheck parameter that let one skip the CRC check > > when attaching a UBI volume. > > > > This also drastically speeds kernel boot by removing a potentially > > useless check, e.g. I gained 3.2s on boot time of a SPEAr600-based board > > for a ~20MB UBI volume used as rootfs. > > Can you give the old and new open/mount time instead of telling how > much you gained on the whole boot-time?
# grabserial -v -d /dev/ttyUSB0 -t "Starting kernel" Kernel command line is: rootfstype=squashfs root=/dev/ubiblock0_0 ubi.mtd=ubi ubi.block=0,rootfs mtdparts=nand:92M@36M(ubi) Current behaviour (CRC checking): [2.335558 0.017867] ubi0: attaching mtd7 [2.504021 0.168463] ubi0: scanning is finished [2.519824 0.015803] ubi0: attached mtd7 (name "ubi", size 92 MiB) [2.523987 0.004163] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 129024 bytes [2.530447 0.006460] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 512 [2.535836 0.005389] ubi0: VID header offset: 512 (aligned 512), data offset: 2048 [2.541601 0.005765] ubi0: good PEBs: 736, bad PEBs: 0, corrupted PEBs: 0 [2.547923 0.006322] ubi0: user volume: 3, internal volumes: 1, max. volumes count: 128 [2.554223 0.006300] ubi0: max/mean erase counter: 1/0, WL threshold: 4096, image sequence number: 463835917 [2.562460 0.008237] ubi0: available PEBs: 0, total reserved PEBs: 736, PEBs reserved for bad PEB handling: 20 [2.569779 0.007319] ubi0: background thread "ubi_bgt0d" started, PID 546 [4.550142 1.980363] block ubiblock0_0: created from ubi0:0(rootfs) Skipping CRC check (ubi.nocheck=0,rootfs): [2.349903 0.019126] ubi0: attaching mtd7 [2.516995 0.167092] ubi0: scanning is finished [2.527101 0.010106] ubi0: skipping CRC check for volume rootfs [2.536719 0.009618] ubi0: attached mtd7 (name "ubi", size 92 MiB) [2.541859 0.005140] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 129024 bytes [2.547744 0.005885] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 512 [2.552990 0.005246] ubi0: VID header offset: 512 (aligned 512), data offset: 2048 [2.560497 0.007507] ubi0: good PEBs: 736, bad PEBs: 0, corrupted PEBs: 0 [2.568010 0.007513] ubi0: user volume: 3, internal volumes: 1, max. volumes count: 128 [2.574723 0.006713] ubi0: max/mean erase counter: 1/0, WL threshold: 4096, image sequence number: 463835917 [2.586223 0.011500] ubi0: available PEBs: 0, total reserved PEBs: 736, PEBs reserved for bad PEB handling: 20 [2.592365 0.006142] ubi0: background thread "ubi_bgt0d" started, PID 545 [2.595960 0.003595] block ubiblock0_0: created from ubi0:0(rootfs) It seems like it's more in the magnitude of 2s rather than 3, but still. This is retrieved from the boot log. Thanks, Quentin
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