| Message ID | fc23172d-3c75-21e2-d551-8b1808cbe593@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] mm: use kvzalloc for swap_info_struct allocation | expand |
On Mon 05-11-18 14:17:01, Vasily Averin wrote: > commit a2468cc9bfdf ("swap: choose swap device according to numa node") > changed 'avail_lists' field of 'struct swap_info_struct' to an array. > In popular linux distros it increased size of swap_info_struct up to > 40 Kbytes and now swap_info_struct allocation requires order-4 page. > Switch to kvzmalloc allows to avoid unexpected allocation failures. While this fixes the most visible issue is this a good long term solution? Aren't we wasting memory without a good reason? IIRC our limit for swap files/devices is much smaller than potential NUMA nodes numbers so we can safely expect that would be only few numa affine nodes. I am not really familiar with the rework which has added numa node awareness but I wouls assueme that we should either go with one global table with a linked list of possible swap_info structure per numa node or use a sparse array. That being said I am not really objecting to this patch as it is simple and backportable to older (stable kernels). I would even dare to add Fixes: a2468cc9bfdf ("swap: choose swap device according to numa node") because not being able to add a swap space on a fragmented system looks like a regression to me. > Acked-by: Aaron Lu <aaron.lu@intel.com> > Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/swapfile.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 644f746e167a..8688ae65ef58 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -2813,7 +2813,7 @@ static struct swap_info_struct *alloc_swap_info(void) > unsigned int type; > int i; > > - p = kzalloc(sizeof(*p), GFP_KERNEL); > + p = kvzalloc(sizeof(*p), GFP_KERNEL); > if (!p) > return ERR_PTR(-ENOMEM); > > @@ -2824,7 +2824,7 @@ static struct swap_info_struct *alloc_swap_info(void) > } > if (type >= MAX_SWAPFILES) { > spin_unlock(&swap_lock); > - kfree(p); > + kvfree(p); > return ERR_PTR(-EPERM); > } > if (type >= nr_swapfiles) { > @@ -2838,7 +2838,7 @@ static struct swap_info_struct *alloc_swap_info(void) > smp_wmb(); > nr_swapfiles++; > } else { > - kfree(p); > + kvfree(p); > p = swap_info[type]; > /* > * Do not memset this entry: a racing procfs swap_next() > -- > 2.17.1
On Mon, Nov 05, 2018 at 03:11:56PM +0100, Michal Hocko wrote: > On Mon 05-11-18 14:17:01, Vasily Averin wrote: > > commit a2468cc9bfdf ("swap: choose swap device according to numa node") > > changed 'avail_lists' field of 'struct swap_info_struct' to an array. > > In popular linux distros it increased size of swap_info_struct up to > > 40 Kbytes and now swap_info_struct allocation requires order-4 page. > > Switch to kvzmalloc allows to avoid unexpected allocation failures. > > While this fixes the most visible issue is this a good long term > solution? Aren't we wasting memory without a good reason? IIRC our limit That's right, we need a better way of handling this in the long term. > for swap files/devices is much smaller than potential NUMA nodes numbers > so we can safely expect that would be only few numa affine nodes. I am > not really familiar with the rework which has added numa node awareness > but I wouls assueme that we should either go with one global table with > a linked list of possible swap_info structure per numa node or use a > sparse array. There is a per-numa-node plist of available swap devices, so every swap device needs an entry on those per-numa-node plist. I think we can convert avail_lists from array to pointer and use vzalloc to allocate the needed memory. MAX_NUMANODES can be used for a simple implementation, or use the precise online node number but then we will need to handle node online/offline events. sparse array sounds promising, I'll take a look, thanks for the pointer. > That being said I am not really objecting to this patch as it is simple > and backportable to older (stable kernels). > > I would even dare to add > Fixes: a2468cc9bfdf ("swap: choose swap device according to numa node") > > because not being able to add a swap space on a fragmented system looks > like a regression to me. Agree, especially it used to work. Regards, Aaron > > Acked-by: Aaron Lu <aaron.lu@intel.com> > > Signed-off-by: Vasily Averin <vvs@virtuozzo.com> > > Acked-by: Michal Hocko <mhocko@suse.com> > > --- > > mm/swapfile.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 644f746e167a..8688ae65ef58 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -2813,7 +2813,7 @@ static struct swap_info_struct *alloc_swap_info(void) > > unsigned int type; > > int i; > > > > - p = kzalloc(sizeof(*p), GFP_KERNEL); > > + p = kvzalloc(sizeof(*p), GFP_KERNEL); > > if (!p) > > return ERR_PTR(-ENOMEM); > > > > @@ -2824,7 +2824,7 @@ static struct swap_info_struct *alloc_swap_info(void) > > } > > if (type >= MAX_SWAPFILES) { > > spin_unlock(&swap_lock); > > - kfree(p); > > + kvfree(p); > > return ERR_PTR(-EPERM); > > } > > if (type >= nr_swapfiles) { > > @@ -2838,7 +2838,7 @@ static struct swap_info_struct *alloc_swap_info(void) > > smp_wmb(); > > nr_swapfiles++; > > } else { > > - kfree(p); > > + kvfree(p); > > p = swap_info[type]; > > /* > > * Do not memset this entry: a racing procfs swap_next() > > -- > > 2.17.1 > > -- > Michal Hocko > SUSE Labs >
diff --git a/mm/swapfile.c b/mm/swapfile.c index 644f746e167a..8688ae65ef58 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2813,7 +2813,7 @@ static struct swap_info_struct *alloc_swap_info(void) unsigned int type; int i; - p = kzalloc(sizeof(*p), GFP_KERNEL); + p = kvzalloc(sizeof(*p), GFP_KERNEL); if (!p) return ERR_PTR(-ENOMEM); @@ -2824,7 +2824,7 @@ static struct swap_info_struct *alloc_swap_info(void) } if (type >= MAX_SWAPFILES) { spin_unlock(&swap_lock); - kfree(p); + kvfree(p); return ERR_PTR(-EPERM); } if (type >= nr_swapfiles) { @@ -2838,7 +2838,7 @@ static struct swap_info_struct *alloc_swap_info(void) smp_wmb(); nr_swapfiles++; } else { - kfree(p); + kvfree(p); p = swap_info[type]; /* * Do not memset this entry: a racing procfs swap_next()
commit a2468cc9bfdf ("swap: choose swap device according to numa node") changed 'avail_lists' field of 'struct swap_info_struct' to an array. In popular linux distros it increased size of swap_info_struct up to 40 Kbytes and now swap_info_struct allocation requires order-4 page. Switch to kvzmalloc allows to avoid unexpected allocation failures. Acked-by: Aaron Lu <aaron.lu@intel.com> Signed-off-by: Vasily Averin <vvs@virtuozzo.com> --- mm/swapfile.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)