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From: Kirill Tkhai <>
To: Miklos Szeredi <>
Subject: Re: [PATCH 3/3] fuse: Use hash table to link processing request
Date: Tue, 25 Sep 2018 12:35:23 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 25.09.2018 12:08, Miklos Szeredi wrote:
> On Tue, Sep 11, 2018 at 12:12 PM, Kirill Tkhai <> wrote:
>> We noticed the performance bottle neck in FUSE running our
>> Virtuozzo storage over rdma. On some types of workload
>> we observe 20% of times pent in request_find() in profiler.
>> This function is iterating over long requests list, and it
>> scales bad.
>> The patch introduces hash table to reduce the number
>> of iterations, we do in this function. Hash generating
>> algorithm is taken from hash_add() function, while
>> 512 lines table is used to store pending requests.
>> This fixes problem and improves the performance.
> Pushed to fuse.git#for-next with a number of small changes.   E.g. I


> reduced the number of cachlines to 256 to make the hashtable size just
> 4k.   Was there a scientific reason for choosing 512 as the optimal
> number of cache lines?

I just tried to choose a size, which is not small for all of potential
users. But, it looks like 256 should be also enough. 
So, there was no hidden mathematics...


  reply	other threads:[~2018-09-25 15:42 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-11 10:11 [PATCH 0/3] fuse: Solve request_find() bottleneck Kirill Tkhai
2018-09-11 10:11 ` [PATCH 1/3] fuse: Change interrupt requests allocation algorhythm Kirill Tkhai
2018-09-11 10:12 ` [PATCH 2/3] fuse: Kill fuse_req::intr_unique Kirill Tkhai
2018-09-11 10:12 ` [PATCH 3/3] fuse: Use hash table to link processing request Kirill Tkhai
2018-09-25  9:08   ` Miklos Szeredi
2018-09-25  9:35     ` Kirill Tkhai [this message]
2018-09-24 12:08 ` [PATCH 0/3] fuse: Solve request_find() bottleneck Kirill Tkhai
2018-09-24 15:04   ` Miklos Szeredi

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