On 1/21/21 1:00 AM, Jason Wang wrote:
>
> On 2021/1/21 13:03, Dongli Zhang wrote:
>> The size of 'struct vhost_scsi' is order-10 (~2.3MB). It may take long time
>> delay by kzalloc() to compact memory pages when there is a lack of
>> high-order pages. As a result, there is latency to create a VM (with
>> vhost-scsi) or to hotadd vhost-scsi-based storage.
>>
>> The prior commit 595cb754983d ("vhost/scsi: use vmalloc for order-10
>> allocation") prefers to fallback only when really needed, while this patch
>> changes allocation to GFP_NOWAIT in order to avoid the delay caused by
>> memory page compact.
>>
>> Cc: Aruna Ramakrishna <aruna.ramakrishna@xxxxxxxxxx>
>> Cc: Joe Jin <joe.jin@xxxxxxxxxx>
>> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
>> ---
>> Another option is to rework by reducing the size of 'struct vhost_scsi',
>> e.g., by replacing inline vhost_scsi.vqs with just memory pointers while
>> each vhost_scsi.vqs[i] should be allocated separately. Please let me
>> know if that option is better.
>>
>> drivers/vhost/scsi.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
>> index 4ce9f00ae10e..85eaa4e883f4 100644
>> --- a/drivers/vhost/scsi.c
>> +++ b/drivers/vhost/scsi.c
>> @@ -1814,7 +1814,7 @@ static int vhost_scsi_open(struct inode *inode, struct
>> file *f)
>> struct vhost_virtqueue **vqs;
>> int r = -ENOMEM, i;
>> - vs = kzalloc(sizeof(*vs), GFP_KERNEL | __GFP_NOWARN |
>> __GFP_RETRY_MAYFAIL);
>> + vs = kzalloc(sizeof(*vs), GFP_NOWAIT | __GFP_NOWARN);
>> if (!vs) {
>> vs = vzalloc(sizeof(*vs));
>> if (!vs)
>
>
> Can we use kvzalloc?
>
Thank you very much for the suggestion.
To use 'GFP_NOWAIT' will avoid any direct compact in __alloc_pages_slowpath(),
while to use kvzalloc() will just avoid retrying direct compact for multiple times.
Although the latter will still do direct compact (without retry), I think it is
better than the former using GFP_NOWAIT.
I will send v2 with kvzalloc().
Thank you very much!
Dongli Zhang
