From ba1ddcb6ca0c46edd275790d1e4e2cfd6219ce19 Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Fri, 8 Jun 2012 11:16:22 +0100 Subject: [PATCH] GFS2: Cache last hash bucket for glock seq_files For the glocks and glstats seq_files, which are exposed via debugfs we should cache the most recent hash bucket, along with the offset into that bucket. This allows us to restart from that point, rather than having to begin at the beginning each time. This is an idea from Eric Dumazet, however I've slightly extended it so that if the position from which we are due to start is at any point beyond the last cached point, we start from the last cached point, plus whatever is the appropriate offset. I don't really expect people to be lseeking around these files, but if they did so with only positive offsets, then we'd still get some of the benefit of using a cached offset. With my simple test of around 200k entries in the file, I'm seeing an approx 10x speed up. Cc: Eric Dumazet Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index 1c4cddf..3ad8cb3 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -46,10 +46,12 @@ #include "trace_gfs2.h" struct gfs2_glock_iter { - int hash; /* hash bucket index */ - struct gfs2_sbd *sdp; /* incore superblock */ - struct gfs2_glock *gl; /* current glock struct */ - char string[512]; /* scratch space */ + int hash; /* hash bucket index */ + unsigned nhash; /* Index within current bucket */ + struct gfs2_sbd *sdp; /* incore superblock */ + struct gfs2_glock *gl; /* current glock struct */ + loff_t last_pos; /* last position */ + char string[512]; /* scratch space */ }; typedef void (*glock_examiner) (struct gfs2_glock * gl); @@ -950,7 +952,7 @@ void gfs2_print_dbg(struct seq_file *seq, const char *fmt, ...) if (seq) { struct gfs2_glock_iter *gi = seq->private; vsprintf(gi->string, fmt, args); - seq_printf(seq, gi->string); + seq_puts(seq, gi->string); } else { vaf.fmt = fmt; vaf.va = &args; @@ -1854,8 +1856,14 @@ static int gfs2_glock_iter_next(struct gfs2_glock_iter *gi) gl = gi->gl; if (gl) { gi->gl = glock_hash_next(gl); + gi->nhash++; } else { + if (gi->hash >= GFS2_GL_HASH_SIZE) { + rcu_read_unlock(); + return 1; + } gi->gl = glock_hash_chain(gi->hash); + gi->nhash = 0; } while (gi->gl == NULL) { gi->hash++; @@ -1864,6 +1872,7 @@ static int gfs2_glock_iter_next(struct gfs2_glock_iter *gi) return 1; } gi->gl = glock_hash_chain(gi->hash); + gi->nhash = 0; } /* Skip entries for other sb and dead entries */ } while (gi->sdp != gi->gl->gl_sbd || atomic_read(&gi->gl->gl_ref) == 0); @@ -1876,7 +1885,12 @@ static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos) struct gfs2_glock_iter *gi = seq->private; loff_t n = *pos; - gi->hash = 0; + if (gi->last_pos <= *pos) + n = gi->nhash + (*pos - gi->last_pos); + else + gi->hash = 0; + + gi->nhash = 0; rcu_read_lock(); do { @@ -1884,6 +1898,7 @@ static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos) return NULL; } while (n--); + gi->last_pos = *pos; return gi->gl; } @@ -1893,7 +1908,7 @@ static void *gfs2_glock_seq_next(struct seq_file *seq, void *iter_ptr, struct gfs2_glock_iter *gi = seq->private; (*pos)++; - + gi->last_pos = *pos; if (gfs2_glock_iter_next(gi)) return NULL; -- 2.7.4