Messages in this thread Patch in this message |  | | | From | Paul Jackson <> | | Date | Wed, 29 Mar 2006 01:11:19 -0800 | | Subject | [PATCH 03/03] Cpuset: memory migration interaction fix |
From: Paul Jackson <pj@sgi.com>
Fix memory migration so that it works regardless of what cpuset the invoking task is in.
If a task invoked a memory migration, by doing one of: 1) writing a different nodemask to a cpuset 'mems' file, or 2) writing a tasks pid to a different cpuset's 'tasks' file, where the cpuset had its 'memory_migrate' option turned on, then the allocation of the new pages for the migrated task(s) was constrained by the invoking tasks cpuset.
If this task wasn't in a cpuset that allowed the requested memory nodes, the memory migration would happen to some other nodes that were in that invoking tasks cpuset. This was usually surprising and puzzling behaviour: Why didn't the pages move? Why did the pages move -there-?
To fix this, temporarilly change the invoking tasks 'mems_allowed' task_struct field to the nodes the migrating tasks is moving to, so that new pages can be allocated there.
Signed-off-by: Paul Jackson <pj@sgi.com> Acked-by: Christoph Lameter <clameter@sgi.com>
--- Finally a fix for this interaction of cpusets with memory migration. I am hoping that this will be suitable for 2.6.17, as memory migration fails in unexpected ways without this fix. -pj
kernel/cpuset.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 52 insertions(+), 5 deletions(-) --- 2.6.16-mm1.orig/kernel/cpuset.c 2006-03-27 08:44:47.894113580 -0800 +++ 2.6.16-mm1/kernel/cpuset.c 2006-03-27 08:47:46.400307814 -0800 @@ -834,6 +834,55 @@ static int update_cpumask(struct cpuset } /* + * cpuset_migrate_mm + * + * Migrate memory region from one set of nodes to another. + * + * Temporarilly set tasks mems_allowed to target nodes of migration, + * so that the migration code can allocate pages on these nodes. + * + * Call holding manage_mutex, so our current->cpuset won't change + * during this call, as manage_mutex holds off any attach_task() + * calls. Therefore we don't need to take task_lock around the + * call to guarantee_online_mems(), as we know no one is changing + * our tasks cpuset. + * + * Hold callback_mutex around the two modifications of our tasks + * mems_allowed to synchronize with cpuset_mems_allowed(). + * + * While the mm_struct we are migrating is typically from some + * other task, the task_struct mems_allowed that we are hacking + * is for our current task, which must allocate new pages for that + * migrating memory region. + * + * We call cpuset_update_task_memory_state() before hacking + * our tasks mems_allowed, so that we are assured of being in + * sync with our tasks cpuset, and in particular, callbacks to + * cpuset_update_task_memory_state() from nested page allocations + * won't see any mismatch of our cpuset and task mems_generation + * values, so won't overwrite our hacked tasks mems_allowed + * nodemask. + */ + +static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from, + const nodemask_t *to) +{ + struct task_struct *tsk = current; + + cpuset_update_task_memory_state(); + + mutex_lock(&callback_mutex); + tsk->mems_allowed = *to; + mutex_unlock(&callback_mutex); + + do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL); + + mutex_lock(&callback_mutex); + guarantee_online_mems(tsk->cpuset, &tsk->mems_allowed); + mutex_unlock(&callback_mutex); +} + +/* * Handle user request to change the 'mems' memory placement * of a cpuset. Needs to validate the request, update the * cpusets mems_allowed and mems_generation, and for each @@ -945,10 +994,8 @@ static int update_nodemask(struct cpuset struct mm_struct *mm = mmarray[i]; mpol_rebind_mm(mm, &cs->mems_allowed); - if (migrate) { - do_migrate_pages(mm, &oldmem, &cs->mems_allowed, - MPOL_MF_MOVE_ALL); - } + if (migrate) + cpuset_migrate_mm(mm, &oldmem, &cs->mems_allowed); mmput(mm); } @@ -1184,7 +1231,7 @@ static int attach_task(struct cpuset *cs if (mm) { mpol_rebind_mm(mm, &to); if (is_memory_migrate(cs)) - do_migrate_pages(mm, &from, &to, MPOL_MF_MOVE_ALL); + cpuset_migrate_mm(mm, &from, &to); mmput(mm); } -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson <pj@sgi.com> 1.650.933.1373 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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