On 2023/9/13 06:44, Dave Chinner wrote: > On Tue, Sep 12, 2023 at 03:20:56PM +0800, Wang Jianchao wrote: >> >> In our production environment, we find that mounting a 500M /boot >> which is umount cleanly needs ~6s. One cause is that ffs() is >> used by xlog_write_log_records() to decide the buffer size. It >> can cause a lot of small IO easily when xlog_clear_stale_blocks() >> needs to wrap around the end of log area and log head block is >> not power of two. Things are similar in xlog_find_verify_cycle(). >> >> The code is able to handed bigger buffer very well, we can use >> roundup_pow_of_two() to replace ffs() directly to avoid small >> and sychronous IOs. >> >> Changes in V1: >> - Also replace the ffs in xlog_find_verify_cycle() > > Change logs go either below the --- line or in the cover letter, > not the commit itself. OK > > Other than that, the change looks ok. The use of ffs() was added in > 2002 simply to make buffers a power-of-2 size. I don't think it had > anything to do with trying to maximise the actual buffer size at > all, otherwise it would have made to use fls() like > roundup_pow_of_two() does... > > Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> > Thanks Jianchao
