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Date:   Thu, 27 Aug 2020 02:55:28 -0700
From:   Eric Dumazet <>
To:     "Li,Rongqing" <>,
        Eric Dumazet <>,
        "" <>,
        "" <>
Subject: Re: [PATCH] iavf: use kvzalloc instead of kzalloc for rx/tx_bi buffer

On 8/27/20 1:53 AM, Li,Rongqing wrote:
>> -----Original Message-----
>> From: Eric Dumazet []
>> Sent: Thursday, August 27, 2020 4:26 PM
>> To: Li,Rongqing <>;;
>> Subject: Re: [PATCH] iavf: use kvzalloc instead of kzalloc for rx/tx_bi buffer
>> On 8/27/20 12:53 AM, Li RongQing wrote:
>>> when changes the rx/tx ring to 4096, kzalloc may fail due to a
>>> temporary shortage on slab entries.
>>> kvmalloc is used to allocate this memory as there is no need to have
>>> this memory area physical continuously.
>>> Signed-off-by: Li RongQing <>
>>> ---
>> Well, fallback to vmalloc() overhead because order-1 pages are not readily
>> available when the NIC is setup (usually one time per boot) is adding TLB cost
>> at run time, for billions of packets to come, maybe for months.
>> Surely trying a bit harder to get order-1 pages is desirable.
>>  __GFP_RETRY_MAYFAIL is supposed to help here.
> Could we add __GFP_RETRY_MAYFAIL to kvmalloc, to ensure the allocation success ?

__GFP_RETRY_MAYFAIL does not _ensure_ the allocation success.

The idea here is that for large allocations (bigger than PAGE_SIZE),
kvmalloc_node() will not force __GFP_NORETRY, meaning that page allocator
will not bailout immediately in case of memory pressure.

This gives a chance for page reclaims to happen, and eventually the high order page
allocation will succeed under normal circumstances.

It is a trade-off, and only worth it for long living allocations.

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