On Fri, 23 Feb 2007 21:03:37 +0900 Tomoki Sekiyama <[EMAIL PROTECTED]> wrote:
> Hi, > > I have observed a problem that write(2) can be blocked for a long time > if a system has several disks and is under heavy I/O pressure. This > patchset is to avoid the problem. > > Example of the probrem: > > There are two processes on a system which has two disks. Process-A > writes heavily to disk-a, and process-B writes small data (e.g. log > files) to disk-b occasionally. A portion of system memory, which is > depends on vm.dirty_ratio (typically 40%), is filled up with Dirty > and Writeback pages of disk-a. > > In this situation, write(2) of process-B could be blocked for a very > long time (more then 60 seconds), although the load of disk-b is quite > low. In particular, the system would become quite slow, if disk-a is > slow (e.g. backup to an USB disk). > > This seems to be the same problem as discussed in LKML: > http://marc.theaimsgroup.com/?t=115559902900003 > and > http://marc.theaimsgroup.com/?t=117182340400003 > Interesting, but how about adjust this parameter like below instead of adding new control knob ?(this kind of knob is not easy to use.) == struct writeback_control wbc = { .bdi = bdi, .sync_mode = WB_SYNC_NONE, .older_than_this = NULL, .nr_to_write = 0, .range_cyclic = 1, }; <snip> if (nr_reclaimable) { /* Just do what I can do */ dirty_pages_on_device = count_dirty_pages_on_device_limited(bdi, writechunk); wbc.nr_to_write = dirty_pages_on_device. writeback_inodes(&wbc); == count_dirty_pages_on_device_limited(bdi, writechunk) above returns dirty pages on bdi. if # of dirty_pages on bdi is larger than writechunk, just returns writechunk. -Kame - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
