From 0be9573a9f9883af83762684a0e27ed5a514041c Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Fri, 26 Nov 2010 14:15:21 +0000 Subject: [PATCH] xenpaging: break endless loop during inital page-out with large pagefiles To allow the starting for xenpaging right after 'xm start XYZ', I specified a pagefile size equal to the guest memory size in the hope to catch more errors where the paged-out state of a p2mt is not checked. While doing that, xenpaging got into an endless loop because some pages cant be paged out right away. Now the policy reports an error if the gfn number wraps. Signed-off-by: Olaf Hering Already-Acked-by: Patrick Colp Already-Acked-by: Keir Fraser --- tools/xenpaging/policy_default.c | 35 +++++++++++++++++++++++++------- tools/xenpaging/xenpaging.c | 7 +++++-- 2 files changed, 33 insertions(+), 9 deletions(-) diff --git a/tools/xenpaging/policy_default.c b/tools/xenpaging/policy_default.c index 1bb89e03ba..5768e691e9 100644 --- a/tools/xenpaging/policy_default.c +++ b/tools/xenpaging/policy_default.c @@ -30,8 +30,12 @@ static unsigned long mru[MRU_SIZE]; -static unsigned int i_mru = 0; +static unsigned int i_mru; static unsigned long *bitmap; +static unsigned long *unconsumed; +static unsigned long current_gfn; +static unsigned long bitmap_size; +static unsigned long max_pages; int policy_init(xenpaging_t *paging) @@ -41,9 +45,17 @@ int policy_init(xenpaging_t *paging) /* Allocate bitmap for pages not to page out */ rc = alloc_bitmap(&bitmap, paging->bitmap_size); + if ( rc != 0 ) + goto out; + /* Allocate bitmap to track unusable pages */ + rc = alloc_bitmap(&unconsumed, paging->bitmap_size); if ( rc != 0 ) goto out; + /* record bitmap_size */ + bitmap_size = paging->bitmap_size; + max_pages = paging->domain_info->max_pages; + /* Initialise MRU list of paged in pages */ for ( i = 0; i < MRU_SIZE; i++ ) mru[i] = INVALID_MFN; @@ -51,8 +63,6 @@ int policy_init(xenpaging_t *paging) /* Don't page out page 0 */ set_bit(0, bitmap); - rc = 0; - out: return rc; } @@ -61,17 +71,27 @@ int policy_choose_victim(xc_interface *xch, xenpaging_t *paging, domid_t domain_id, xenpaging_victim_t *victim) { + unsigned long wrap = current_gfn; ASSERT(victim != NULL); /* Domain to pick on */ victim->domain_id = domain_id; - + do { - /* Randomly choose a gfn to evict */ - victim->gfn = rand() % paging->domain_info->max_pages; + current_gfn++; + if ( current_gfn >= max_pages ) + current_gfn = 0; + if ( wrap == current_gfn ) + { + victim->gfn = INVALID_MFN; + return -ENOSPC; + } } - while ( test_bit(victim->gfn, bitmap) ); + while ( test_bit(current_gfn, bitmap) || test_bit(current_gfn, unconsumed) ); + + set_bit(current_gfn, unconsumed); + victim->gfn = current_gfn; return 0; } @@ -79,6 +99,7 @@ int policy_choose_victim(xc_interface *xch, void policy_notify_paged_out(domid_t domain_id, unsigned long gfn) { set_bit(gfn, bitmap); + clear_bit(gfn, unconsumed); } void policy_notify_paged_in(domid_t domain_id, unsigned long gfn) diff --git a/tools/xenpaging/xenpaging.c b/tools/xenpaging/xenpaging.c index b3b579ef96..778537bd5c 100644 --- a/tools/xenpaging/xenpaging.c +++ b/tools/xenpaging/xenpaging.c @@ -446,7 +446,8 @@ static int evict_victim(xc_interface *xch, xenpaging_t *paging, domid_t domain_i ret = policy_choose_victim(xch, paging, domain_id, victim); if ( ret != 0 ) { - ERROR("Error choosing victim"); + if ( ret != -ENOSPC ) + ERROR("Error choosing victim"); goto out; } @@ -525,7 +526,9 @@ int main(int argc, char *argv[]) memset(victims, 0, sizeof(xenpaging_victim_t) * num_pages); for ( i = 0; i < num_pages; i++ ) { - evict_victim(xch, paging, domain_id, &victims[i], fd, i); + rc = evict_victim(xch, paging, domain_id, &victims[i], fd, i); + if ( rc == -ENOSPC ) + break; if ( i % 100 == 0 ) DPRINTF("%d pages evicted\n", i); } -- 2.30.2