[Fwd: Re: Caching of reads]

[Alex J Lennon]

>Strange. JFFS2 doesn't do caching - that's supposed to be handle by the
>Linux VFS/VM. But set CONFIG_JFFS2_FS_DEBUG=1 and
>echo 9 > /proc/sys/kernel/printk, then see what it's actually being asked
>to read each time.

An strace seems to show it's related to the fork(), shortly after the fork()
?

-Alex

--- SIGCHLD (Child exited) ---
wait4(-1, 0xbffff840, WNOHANG, NULL)    = -1 ECHILD (No child processes)
sigreturn()                             = ? (mask now [])
rt_sigaction(SIGINT, {SIG_DFL}, {0x806c32c, [], 0x4000000}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
stat("/bin/sleep", <7>Node read from 00d9d8f4: node_crc f3b6e771, calculated
CRC
 f3b6e771. dsize 7, csize 7, offset 0, buf c3be1ea0
{st_mode=S_IFREG|0755, st_size=132432, ...}) = 0
rt_sigprocmask(SIG_BLOCK, [INT CHLD], [], 8) = 0
fork(<7>Node read from 00d9d8f4: node_crc f3b6e771, calculated CRC f3b6e771.
dsi
ze 7, csize 7, offset 0, buf c3be1ea0
<7>Node read from 00cec5c0: node_crc b16a4fa6, calculated CRC b16a4fa6.
dsize b,
 csize b, offset 0, buf c3beec60
<7>Node read from 00c55d1c: node_crc 544bdb58, calculated CRC 544bdb58.
dsize d,
 csize d, offset 0, buf c3be1ea0
)                                  = 841
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [CHLD], 8) = 0
rt_sigprocmask(SIG_SETMASK, [CHLD], NULL, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGINT, {0x806c32c, [], 0x4000000}, {SIG_DFL}, 8) = 0
wait4(-1, [WIFEXITED(s) && WEXITSTATUS(s) == 0], 0, NULL) = 841
rt_sigprocmask(SIG_BLOCK, [CHLD TTOU], [CHLD], 8) = 0
rt_sigprocmask(SIG_SETMASK, [CHLD], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [CHLD], 8) = 0
rt_sigprocmask(SIG_SETMASK, [CHLD], NULL, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
--- SIGCHLD (Child exited) ---
wait4(-1, 0xbffff840, WNOHANG, NULL)    = -1 ECHILD (No child processes)
sigreturn()                             = ? (mask now [])
rt_sigaction(SIGINT, {SIG_DFL}, {0x806c32c, [], 0x4000000}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
stat("/bin/sleep", <7>Node read from 00d9d8f4: node_crc f3b6e771, calculated
CRC
 f3b6e771. dsize 7, csize 7, offset 0, buf c3be1ea0
{st_mode=S_IFREG|0755, st_size=132432, ...}) = 0
rt_sigprocmask(SIG_BLOCK, [INT CHLD], [], 8) = 0
fork(<7>Node read from 00d9d8f4: node_crc f3b6e771, calculated CRC f3b6e771.
dsi
ze 7, csize 7, offset 0, buf c3be1ea0
<7>Node read from 00cec5c0: node_crc b16a4fa6, calculated CRC b16a4fa6.
dsize b,
 csize b, offset 0, buf c3beec60
<7>Node read from 00c55d1c: node_crc 544bdb58, calculated CRC 544bdb58.
dsize d,
 csize d, offset 0, buf c3be1ea0
)                                  = 842
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [CHLD], 8) = 0
rt_sigprocmask(SIG_SETMASK, [CHLD], NULL, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGINT, {0x806c32c, [], 0x4000000}, {SIG_DFL}, 8) = 0
wait4(-1, [WIFEXITED(s) && WEXITSTATUS(s) == 0], 0, NULL) = 842
rt_sigprocmask(SIG_BLOCK, [CHLD TTOU], [CHLD], 8) = 0
rt_sigprocmask(SIG_SETMASK, [CHLD], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [CHLD], 8) = 0
rt_sigprocmask(SIG_SETMASK, [CHLD], NULL, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0


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