From 03be4100fb3cbbad1c0d1704b0b8dd81f63f63fb Mon Sep 17 00:00:00 2001 From: Olaf Hering Date: Mon, 20 Feb 2012 21:18:44 +0100 Subject: xenpaging: improve performance in policy_choose_victim policy_choose_victim() is one of the bottlenecks in xenpaging. It is called alot to find free bits in the fragmented bitmaps. Reduce turnaround time by skipping longs with all bits set. Adjust wrap detection in loop. v2: - fix copy&paste error, bitmap was tested twice Signed-off-by: Olaf Hering Committed-by: Ian Jackson --- tools/xenpaging/policy_default.c | 57 +++++++++++++++++++++++++++++----------- 1 file changed, 41 insertions(+), 16 deletions(-) (limited to 'tools/xenpaging') diff --git a/tools/xenpaging/policy_default.c b/tools/xenpaging/policy_default.c index 7563720092..4648456031 100644 --- a/tools/xenpaging/policy_default.c +++ b/tools/xenpaging/policy_default.c @@ -80,33 +80,58 @@ int policy_init(struct xenpaging *paging) unsigned long policy_choose_victim(struct xenpaging *paging) { xc_interface *xch = paging->xc_handle; - unsigned long wrap = current_gfn; + unsigned long i; - do + /* One iteration over all possible gfns */ + for ( i = 0; i < max_pages; i++ ) { + /* Try next gfn */ current_gfn++; + + /* Restart on wrap */ if ( current_gfn >= max_pages ) current_gfn = 0; - /* Could not nominate any gfn */ - if ( wrap == current_gfn ) + + if ( (current_gfn & (BITS_PER_LONG - 1)) == 0 ) { - paging->use_poll_timeout = 1; - /* Count wrap arounds */ - unconsumed_cleared++; - /* Force retry every few seconds (depends on poll() timeout) */ - if ( unconsumed_cleared > 123) + /* All gfns busy */ + if ( ~bitmap[current_gfn >> ORDER_LONG] == 0 || ~unconsumed[current_gfn >> ORDER_LONG] == 0 ) { - /* Force retry of unconsumed gfns */ - bitmap_clear(unconsumed, max_pages); - unconsumed_cleared = 0; - DPRINTF("clearing unconsumed, wrap %lx", wrap); - /* One more round before returning ENOSPC */ + current_gfn += BITS_PER_LONG; + i += BITS_PER_LONG; continue; } - return INVALID_MFN; } + + /* gfn busy */ + if ( test_bit(current_gfn, bitmap) ) + continue; + + /* gfn already tested */ + if ( test_bit(current_gfn, unconsumed) ) + continue; + + /* gfn found */ + break; + } + + /* Could not nominate any gfn */ + if ( i >= max_pages ) + { + /* No more pages, wait in poll */ + paging->use_poll_timeout = 1; + /* Count wrap arounds */ + unconsumed_cleared++; + /* Force retry every few seconds (depends on poll() timeout) */ + if ( unconsumed_cleared > 123) + { + /* Force retry of unconsumed gfns on next call */ + bitmap_clear(unconsumed, max_pages); + unconsumed_cleared = 0; + DPRINTF("clearing unconsumed, current_gfn %lx", current_gfn); + } + return INVALID_MFN; } - while ( test_bit(current_gfn, bitmap) || test_bit(current_gfn, unconsumed) ); set_bit(current_gfn, unconsumed); return current_gfn; -- cgit v1.2.3