On Tue, Mar 27 2007, Ming Zhang wrote: > On Tue, 2007-03-27 at 12:58 +0200, Jens Axboe wrote: > > On Sun, Mar 25 2007, Ming Zhang wrote: > > > Hi All > > > > > > I am using blktrace to trace a untar operation on a 400GB (already 80% > > > used) ext3 disk. > > > > > > since journal in ext3 is at the beginning of ext3, so small LBA are > > > journal operations, and large lba should be inode or file data. > > > > > > 8,0 0 1081156 60.171965751 4929 P R [kjournald] > > > 8,0 0 1081157 60.171965991 4929 I W 26079 + 8 [kjournald] > > > 8,0 0 1081158 60.171966726 4929 U R [kjournald] 1 > > > 8,0 0 1081159 60.171968511 4929 D W 26079 + 8 [kjournald] > > > 8,0 0 1081160 60.172249031 0 C W 26079 + 8 [0] > > > > > > journal request > > > > > > 8,0 0 1081161 60.172306613 4944 Q W 733338903 + 8 [tar] > > > 8,0 0 1081162 60.172307471 4944 G W 733338903 + 8 [tar] > > > 8,0 0 1081163 60.172308435 4944 P R [tar] > > > 8,0 0 1081164 60.172308798 4944 I W 733338903 + 8 [tar] > > > 8,0 0 1081165 60.172311794 4944 Q W 733338911 + 8 [tar] > > > 8,0 0 1081166 60.172312274 4944 M W 733338911 + 8 [tar] > > > > > > file or inode > > > > > > 8,0 0 1081167 60.172327693 4929 U R [kjournald] 1 > > > > > > why here a R(read) come up? and what is the meaning of this "1" here? > > > > It's not a read, it's an UNPLUG. And the 1 means that there was 1 > > request plugged when it happened. > > > > > 8,0 0 1081168 60.172329564 4929 D W 733338903 + 16 > > > [kjournald] > > > 8,0 0 1081169 60.172773400 0 C W 733338903 + 16 [0] > > > > > > why it is kjounrald here to "D" this request? is this because tar > > > already "finish" the request by writing to page cache and then when do > > > device io, current process is happened to be kjournald? i read the code > > > and it grabs current pid, so it looks so. but i still need a > > > confirmation here from your guys. > > > > Because kjournald apparently ends up doing the dispatch. The unplug will > > cause dispatch of requests, and kjournald did the unplug. So it gets to > > do the dispatching as well. > > > > why kjournald do the unplug? from the name i thought it is only for > journal (jbd)? then what pdflush does? thx.
kjournald does do io, hence it may get involved with plugging/unplugging. pdflush writes out background data, other processes may be tasks with writing out data as well. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-btrace" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
