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From: Jameson Miller <jameson.miller81@gmail.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: Jameson Miller <jamill@microsoft.com>,
	"git@vger.kernel.org" <git@vger.kernel.org>,
	"gitster@pobox.com" <gitster@pobox.com>,
	"pclouds@gmail.com" <pclouds@gmail.com>
Subject: Re: [PATCH v1 3/5] mem-pool: fill out functionality
Date: Mon, 23 Apr 2018 14:20:14 -0400	[thread overview]
Message-ID: <5584faf6-23a0-366a-bd87-cf9e420f212c@gmail.com> (raw)
In-Reply-To: <20180423104931.c465b6a260219c96feba41ff@google.com>



On 04/23/2018 01:49 PM, Jonathan Tan wrote:
> On Mon, 23 Apr 2018 13:27:09 -0400
> Jameson Miller <jameson.miller81@gmail.com> wrote:
> 
>>> This seems overly complicated - the struct mem_pool already has a linked
>>> list of pages, so couldn't you create a custom page and insert it behind
>>> the current front page instead whenever you needed a large-size page?
>>
>> Yes - that is another option. However, the linked list of pages includes
>> memory that *could* have space for an allocation, while the "custom"
>> region will never have left over memory that can be used for other
>> allocations. When searching pages for memory to satisfy a request, there
>> is no reason to search through the "custom" pages. There is a trade-off
>> between complexity and implementation, so I am open to suggestions.
>>
>> This was discussed in [1], where it originally was implemented closer to
>> what you describe here.
>>
>>> Also, when combining, there could be some wasted space on one of the
>>> pages. I'm not sure if that's worth calling out, though.
>>
>> Yes, we bring over the whole page. However, these pages are now
>> available for new allocations.
>>
>> [1]
>> https://public-inbox.org/git/xmqqk1u2k91l.fsf@gitster-ct.c.googlers.com/
> 
> Ah, I didn't realize that the plan was to search over all pages when
> allocating memory from the pool, instead of only searching the last
> page. This seems like a departure from the fast-import.c way, where as
> far as I can tell, new_object() searches only one page. If we do plan to
> do this, searching all pages doesn't seem like a good idea to me,
> especially since the objects we're storing in the pool are of similar
> size.

I see. However, the new_object() logic in fast-import is a different 
than the logic mem_pool was abstracting, and is not covered by the 
mem_pool functionality. The behavior of searching over all pages for one 
to satisfy the request existed previously and was not changed in the 
mem_pool implementation.

> 
> If we decide to go ahead with searching all the pages, though, the
> "custom" pages should probably be another linked list instead of an
> array.
> 

This is an option - I went with the current design because we only need 
pointers to a block of memory (as well tracking how large the allocation 
is for verification purposes). We don't necessarily need the extra 
overhead of a structure to track the linked list nodes, when it is 
provided by the existing array manipulation functions. I am open to 
feedback on this point, however.


  reply	other threads:[~2018-04-23 18:20 UTC|newest]

Thread overview: 100+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-17 16:34 [PATCH v1 0/5] Allocate cache entries from memory pool Jameson Miller
2018-04-17 16:34 ` Jameson Miller
2018-04-17 16:34 ` [PATCH v1 1/5] read-cache: teach refresh_cache_entry to take istate Jameson Miller
2018-04-17 19:00   ` Ben Peart
2018-04-17 16:34 ` [PATCH v1 2/5] Add an API creating / discarding cache_entry structs Jameson Miller
2018-04-17 23:11   ` Ben Peart
2018-04-17 16:34 ` [PATCH v1 4/5] Allocate cache entries from memory pools Jameson Miller
2018-04-17 16:34 ` [PATCH v1 3/5] mem-pool: fill out functionality Jameson Miller
2018-04-20 23:21   ` Jonathan Tan
2018-04-23 17:27     ` Jameson Miller
2018-04-23 17:49       ` Jonathan Tan
2018-04-23 18:20         ` Jameson Miller [this message]
2018-04-17 16:34 ` [PATCH v1 5/5] Add optional memory validations around cache_entry lifecyle Jameson Miller
2018-04-17 18:39 ` [PATCH v1 0/5] Allocate cache entries from memory pool Ben Peart
2018-04-23 14:09   ` Jameson Miller
2018-04-18  4:49 ` Junio C Hamano
2018-04-20 17:49   ` Stefan Beller
2018-04-23 16:44     ` Jameson Miller
2018-04-23 17:18       ` Stefan Beller
2018-04-23 16:19   ` Jameson Miller
2018-04-20 23:34 ` Jonathan Tan
2018-04-23 17:14   ` Jameson Miller
2018-04-30 15:31 ` [PATCH v2 " Jameson Miller
2018-04-30 15:31   ` [PATCH v2 1/5] read-cache: teach refresh_cache_entry() to take istate Jameson Miller
2018-04-30 15:31   ` [PATCH v2 2/5] block alloc: add lifecycle APIs for cache_entry structs Jameson Miller
2018-04-30 15:31   ` [PATCH v2 3/5] mem-pool: fill out functionality Jameson Miller
2018-04-30 21:42     ` Stefan Beller
2018-05-01 15:43       ` Jameson Miller
2018-05-03 16:18     ` Duy Nguyen
2018-04-30 15:31   ` [PATCH v2 4/5] block alloc: allocate cache entries from mem_pool Jameson Miller
2018-04-30 15:31   ` [PATCH v2 5/5] block alloc: add validations around cache_entry lifecyle Jameson Miller
2018-05-03 16:28     ` Duy Nguyen
2018-05-03 16:35   ` [PATCH v2 0/5] Allocate cache entries from memory pool Duy Nguyen
2018-05-03 17:21     ` Stefan Beller
2018-05-03 19:17       ` Duy Nguyen
2018-05-03 20:58         ` Stefan Beller
2018-05-03 21:13           ` Jameson Miller
2018-05-03 22:18             ` [PATCH] alloc.c: replace alloc by mempool Stefan Beller
2018-05-04 16:33               ` Duy Nguyen
2018-05-08  0:37                 ` Junio C Hamano
2018-05-08  0:44                   ` Stefan Beller
2018-05-08  1:07                     ` Junio C Hamano
2018-05-23 14:47 ` [PATCH v3 0/7] allocate cache entries from memory pool Jameson Miller
2018-05-23 14:47   ` [PATCH v3 1/7] read-cache: teach refresh_cache_entry() to take istate Jameson Miller
2018-05-25 22:54     ` Stefan Beller
2018-05-23 14:47   ` [PATCH v3 2/7] block alloc: add lifecycle APIs for cache_entry structs Jameson Miller
2018-05-24  4:52     ` Junio C Hamano
2018-05-24 14:47       ` Jameson Miller
2018-05-23 14:47   ` [PATCH v3 3/7] mem-pool: only search head block for available space Jameson Miller
2018-05-23 14:47   ` [PATCH v3 4/7] mem-pool: add lifecycle management functions Jameson Miller
2018-05-23 14:47   ` [PATCH v3 5/7] mem-pool: fill out functionality Jameson Miller
2018-06-01 19:28     ` Stefan Beller
2018-05-23 14:47   ` [PATCH v3 6/7] block alloc: allocate cache entries from mem_pool Jameson Miller
2018-05-23 14:47   ` [PATCH v3 7/7] block alloc: add validations around cache_entry lifecyle Jameson Miller
2018-05-24  4:55   ` [PATCH v3 0/7] allocate cache entries from memory pool Junio C Hamano
2018-05-24 14:44     ` Jameson Miller
2018-05-25 22:53       ` Stefan Beller
2018-06-20 20:41         ` Jameson Miller
2018-05-25 22:41   ` Stefan Beller
2018-06-20 20:17 ` [PATCH v4 0/8] Allocate cache entries from mem_pool Jameson Miller
2018-06-20 20:17   ` [PATCH v4 1/8] read-cache: teach refresh_cache_entry() to take istate Jameson Miller
2018-06-20 20:17   ` [PATCH v4 2/8] block alloc: add lifecycle APIs for cache_entry structs Jameson Miller
2018-06-21 21:14     ` Stefan Beller
2018-06-28 14:07       ` Jameson Miller
2018-06-20 20:17   ` [PATCH v4 3/8] mem-pool: only search head block for available space Jameson Miller
2018-06-21 21:33     ` Stefan Beller
2018-06-28 14:12       ` Jameson Miller
2018-06-20 20:17   ` [PATCH v4 4/8] mem-pool: tweak math on mp_block allocation size Jameson Miller
2018-06-20 20:17   ` [PATCH v4 5/8] mem-pool: add lifecycle management functions Jameson Miller
2018-06-20 20:17   ` [PATCH v4 6/8] mem-pool: fill out functionality Jameson Miller
2018-06-20 20:17   ` [PATCH v4 7/8] block alloc: allocate cache entries from mem_pool Jameson Miller
2018-06-20 20:17   ` [PATCH v4 8/8] block alloc: add validations around cache_entry lifecyle Jameson Miller
2018-06-28 14:00   ` [PATCH v5 0/8] Allocate cache entries from mem_pool Jameson Miller
2018-06-28 14:00     ` [PATCH v5 1/8] read-cache: teach refresh_cache_entry() to take istate Jameson Miller
2018-06-28 14:00     ` [PATCH v5 2/8] read-cache: make_cache_entry should take object_id struct Jameson Miller
2018-06-28 17:14       ` Junio C Hamano
2018-06-28 22:27       ` SZEDER Gábor
2018-06-28 14:00     ` [PATCH v5 3/8] block alloc: add lifecycle APIs for cache_entry structs Jameson Miller
2018-06-28 18:43       ` Junio C Hamano
2018-06-28 22:28       ` SZEDER Gábor
2018-06-28 14:00     ` [PATCH v5 4/8] mem-pool: only search head block for available space Jameson Miller
2018-06-28 14:00     ` [PATCH v5 5/8] mem-pool: add life cycle management functions Jameson Miller
2018-06-28 17:15       ` Junio C Hamano
2018-06-28 14:00     ` [PATCH v5 6/8] mem-pool: fill out functionality Jameson Miller
2018-06-28 19:09       ` Junio C Hamano
2018-07-02 18:28         ` Jameson Miller
2018-06-28 14:00     ` [PATCH v5 7/8] block alloc: allocate cache entries from mem-pool Jameson Miller
2018-06-28 14:00     ` [PATCH v5 8/8] block alloc: add validations around cache_entry lifecyle Jameson Miller
2018-07-02 19:49     ` [PATCH v6 0/8] Allocate cache entries from mem_pool Jameson Miller
2018-07-02 19:49       ` [PATCH v6 1/8] read-cache: teach refresh_cache_entry to take istate Jameson Miller
2018-07-02 19:49       ` [PATCH v6 2/8] read-cache: teach make_cache_entry to take object_id Jameson Miller
2018-07-02 21:23         ` Stefan Beller
2018-07-05 15:20           ` Jameson Miller
2018-07-02 19:49       ` [PATCH v6 3/8] block alloc: add lifecycle APIs for cache_entry structs Jameson Miller
2018-07-22  9:23         ` Duy Nguyen
2018-07-02 19:49       ` [PATCH v6 4/8] mem-pool: only search head block for available space Jameson Miller
2018-07-02 19:49       ` [PATCH v6 5/8] mem-pool: add life cycle management functions Jameson Miller
2018-07-02 19:49       ` [PATCH v6 6/8] mem-pool: fill out functionality Jameson Miller
2018-07-02 19:49       ` [PATCH v6 7/8] block alloc: allocate cache entries from mem_pool Jameson Miller
2018-07-02 19:49       ` [PATCH v6 8/8] block alloc: add validations around cache_entry lifecyle Jameson Miller

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