On Tue, May 10, 2022 at 9:19 PM Xiongwei Song <sxwjean@xxxxxxxxx> wrote:
>
> On Tue, May 10, 2022 at 8:47 PM Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote:
> >
> > On Tue, May 10, 2022 at 8:31 PM Xiongwei Song <sxwjean@xxxxxxxxx> wrote:
> > >
> > > Hi Hsin-Yi,
> > >
> > > On Mon, May 9, 2022 at 10:29 PM Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote:
> > > >
> > > > On Mon, May 9, 2022 at 9:21 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > On Mon, May 09, 2022 at 08:43:45PM +0800, Xiongwei Song wrote:
> > > > > > Hi Hsin-Yi and Matthew,
> > > > > >
> > > > > > With the patch from the attachment on linux 5.10, ran the command as I
> > > > > > mentioned earlier,
> > > > > > got the results below:
> > > > > > 1:40.65 (1m + 40.65s)
> > > > > > 1:10.12
> > > > > > 1:11.10
> > > > > > 1:11.47
> > > > > > 1:11.59
> > > > > > 1:11.94
> > > > > > 1:11.86
> > > > > > 1:12.04
> > > > > > 1:12.21
> > > > > > 1:12.06
> > > > > >
> > > > > > The performance has improved obviously, but compared to linux 4.18, the
> > > > > > performance is not so good.
> > > > > >
> > > > I think you shouldn't compare the performance with 4.18 directly,
> > > > since there might be other factors that impact the performance.
> > >
> > > Make sense.
> > >
> > > >I'd suggest comparing the same kernel version with:
> > > > a) with this patch
> > > > b) with c1f6925e1091 ("mm: put readahead pages in cache earlier") reverted.
> > >
> > > With 9eec1d897139 ("squashfs: provide backing_dev_info in order to disable
> > > read-ahead") reverted and applied 0001-WIP-squashfs-implement-readahead.patch,
> > > test result on linux 5.18：
> > > 1:41.51 (1m + 41.51s)
> > > 1:08.11
> > > 1:10.37
> > > 1:11.17
> > > 1:11.32
> > > 1:11.59
> > > 1:12.23
> > > 1:12.08
> > > 1:12.76
> > > 1:12.51
> > >
> > > performance worse 1 ~ 2s than linux 5.18 vanilla.
> > >
> >
> > Can you share the pack file you used for testing? Thanks
>
> You are saying the files that are put in squashfs partitions? If yes, I can tell
> I just put some dynamic libraries in partitions:
> -rwxr-xr-x 1 root root 200680 Apr 20 03:57 ld-2.33.so
> lrwxrwxrwx 1 root root 10 Apr 20 03:57 ld-linux-x86-64.so.2 -> ld-2.33.so
> -rwxr-xr-x 1 root root 18776 Apr 20 03:57 libanl-2.33.so
> lrwxrwxrwx 1 root root 14 Apr 20 03:57 libanl.so.1 -> libanl-2.33.so
> lrwxrwxrwx 1 root root 17 Apr 20 04:08 libblkid.so.1 -> libblkid.so.1.1.0
> -rwxr-xr-x 1 root root 330776 Apr 20 04:08 libblkid.so.1.1.0
> -rwxr-xr-x 1 root root 1823192 Apr 20 03:57 libc-2.33.so
> ...... snip ......
>
> The number of files is 110(55 libs + 55 soft links to libs). I have 90 squashfs
> partitions which save the identical files. The space of each partition is 11M,
> nothing special.
>
> Thanks.
>
I noticed that there's a crash at
https://elixir.bootlin.com/linux/latest/source/lib/lzo/lzo1x_decompress_safe.c#L218
when testing on my system.
(I have CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS enabled)
Full logs:
[ 119.062420] Unable to handle kernel paging request at virtual
address ffffffc017337000
[ 119.062437] Mem abort info:
[ 119.062442] ESR = 0x96000047
[ 119.062447] EC = 0x25: DABT (current EL), IL = 32 bits
[ 119.062451] SET = 0, FnV = 0
[ 119.062454] EA = 0, S1PTW = 0
[ 119.062457] Data abort info:
[ 119.062460] ISV = 0, ISS = 0x00000047
[ 119.062464] CM = 0, WnR = 1
[ 119.062469] swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000041099000
[ 119.062473] [ffffffc017337000] pgd=000000010014a003,
p4d=000000010014a003, pud=000000010014a003, pmd=000000010ba59003,
pte=0000000000000000
[ 119.062489] Internal error: Oops: 96000047 [#1] PREEMPT SMP
[ 119.062494] Modules linked in: vhost_vsock vhost vhost_iotlb
vmw_vsock_virtio_transport_common vsock rfcomm algif_hash
algif_skcipher af_alg veth uinput xt_cgroup mtk_dip mtk_cam_isp
mtk_vcodec_enc mtk_vcodec_dec hci_uart mtk_fd mtk_mdp3 v4l2_h264
mtk_vcodec_common mtk_vpu xt_MASQUERADE mtk_jpeg cros_ec_rpmsg btqca
videobuf2_dma_contig v4l2_fwnode v4l2_mem2mem btrtl elants_i2c mtk_scp
mtk_rpmsg rpmsg_core mtk_scp_ipi mt8183_cci_devfreq ip6table_nat fuse
8021q bluetooth ecdh_generic ecc iio_trig_sysfs cros_ec_lid_angle
cros_ec_sensors cros_ec_sensors_core industrialio_triggered_buffer
kfifo_buf cros_ec_sensorhub cros_ec_typec typec hid_google_hammer
ath10k_sdio lzo_rle lzo_compress ath10k_core ath mac80211 zram
cfg80211 uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2
videobuf2_common cdc_ether usbnet r8152 mii joydev
[ 119.062613] CPU: 4 PID: 4161 Comm: chrome Tainted: G W
5.10.112 #105 39f11bffda227eaae4c704733b9bf01db22d8b4d
[ 119.062617] Hardware name: Google burnet board (DT)
[ 119.062623] pstate: 20400005 (nzCv daif +PAN -UAO -TCO BTYPE=--)
[ 119.062636] pc : lzo1x_decompress_safe+0x1dc/0x564
[ 119.062643] lr : lzo_uncompress+0x134/0x1f0
[ 119.062647] sp : ffffffc01837b860
[ 119.062650] x29: ffffffc01837b860 x28: 0000000000000000
[ 119.062656] x27: 0000000000005451 x26: ffffffc0171c9445
[ 119.062662] x25: 0000000000000000 x24: ffffffc017437000
[ 119.062668] x23: ffffffc0171c944f x22: ffffffc017136000
[ 119.062673] x21: ffffffc017336ff1 x20: ffffffc017237000
[ 119.062679] x19: ffffffc01837b8d0 x18: 0000000000000000
[ 119.062684] x17: 00000000000001eb x16: 0000000000000012
[ 119.062689] x15: 000000000010000f x14: d600120202000001
[ 119.062695] x13: ffffffc017336ff1 x12: ffffffc017336ff4
[ 119.062700] x11: 0000000000000002 x10: 01010101010100ff
[ 119.062705] x9 : ffffffffffffffff x8 : ffffffc0171c944d
[ 119.062710] x7 : d15d3aaabd294330 x6 : 0206397115fe28ab
[ 119.062715] x5 : ffffffc0171c944f x4 : 000000000009344f
[ 119.062721] x3 : ffffffc01837b8d0 x2 : ffffffc017237000
[ 119.062726] x1 : 000000000009344f x0 : ffffffc0171c9447
[ 119.062731] Call trace:
[ 119.062738] lzo1x_decompress_safe+0x1dc/0x564
[ 119.062742] lzo_uncompress+0x134/0x1f0
[ 119.062746] squashfs_decompress+0x6c/0xb4
[ 119.062753] squashfs_read_data+0x1a8/0x298
[ 119.062758] squashfs_readahead+0x308/0x474
[ 119.062765] read_pages+0x74/0x280
[ 119.062769] page_cache_ra_unbounded+0x1d0/0x228
[ 119.062773] do_page_cache_ra+0x44/0x50
[ 119.062779] do_sync_mmap_readahead+0x188/0x1a0
[ 119.062783] filemap_fault+0x100/0x350
[ 119.062789] __do_fault+0x48/0x10c
[ 119.062793] do_cow_fault+0x58/0x12c
[ 119.062797] handle_mm_fault+0x544/0x904
[ 119.062804] do_page_fault+0x260/0x384
[ 119.062809] do_translation_fault+0x44/0x5c
[ 119.062813] do_mem_abort+0x48/0xb4
[ 119.062819] el0_da+0x28/0x34
[ 119.062824] el0_sync_compat_handler+0xb8/0xcc
[ 119.062829] el0_sync_compat+0x188/0x1c0
[ 119.062837] Code: f94001ae f90002ae f94005ae 910041ad (f90006ae)
[ 119.062842] ---[ end trace 3e9828c7360fd7be ]---
[ 119.090436] Kernel panic - not syncing: Oops: Fatal exception
[ 119.090455] SMP: stopping secondary CPUs
[ 119.090467] Kernel Offset: 0x2729c00000 from 0xffffffc010000000
[ 119.090471] PHYS_OFFSET: 0xffffffd880000000
[ 119.090477] CPU features: 0x08240002,2188200c
1) Traces near when the crash happened:
[ 79.495580] Block @ 0x60eea9c, compressed size 65744, src size 1048576
[ 80.363573] Block @ 0x1f9f000, compressed size 200598, src size 1048576
[ 80.371256] Block @ 0x1fcff96, compressed size 80772, src size 1048576
[ 80.428388] Block @ 0x1fe3b1a, compressed size 83941, src size 1048576
[ 80.435319] Block @ 0x1ff82ff, compressed size 77936, src size 1048576
[ 80.724331] Block @ 0x4501000, compressed size 364069, src size 1048576
[ 80.738683] Block @ 0x4dccf28, compressed size 603215, src size 2097152
It's also noticed that when the crash happened, nr_pages obtained by
readahead_count() is 512.
nr_pages = readahead_count(ractl); // this line
2) Normal cases that won't crash:
[ 22.651750] Block @ 0xb3bbca6, compressed size 42172, src size 262144
[ 22.653580] Block @ 0xb3c6162, compressed size 29815, src size 262144
[ 22.656692] Block @ 0xb4a293f, compressed size 17484, src size 131072
[ 22.666099] Block @ 0xb593881, compressed size 39742, src size 262144
[ 22.668699] Block @ 0xb59d3bf, compressed size 37841, src size 262144
[ 22.695739] Block @ 0x13698673, compressed size 65907, src size 131072
[ 22.698619] Block @ 0x136a87e6, compressed size 3155, src size 131072
[ 22.703400] Block @ 0xb1babe8, compressed size 99391, src size 131072
[ 22.706288] Block @ 0x1514abc6, compressed size 4627, src size 131072
nr_pages are observed to be 32, 64, 256... These won't cause a crash.
Other values (max_pages, bsize, block...) looks normal
I'm not sure why the crash happened, but I tried to modify the mask
for a bit. After modifying the mask value to below, the crash is gone
(nr_pages are <=256).
Based on my testing on a 300K pack file, there's no performance change.
diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index 20ec48cf97c5..f6d9b6f88ed9 100644
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -499,8 +499,8 @@ static void squashfs_readahead(struct
readahead_control *ractl)
{
struct inode *inode = ractl->mapping->host;
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
- size_t mask = (1UL << msblk->block_log) - 1;
size_t shift = msblk->block_log - PAGE_SHIFT;
+ size_t mask = (1UL << shift) - 1;
Any pointers are appreciated. Thanks!
