From: Jameson Miller Date: Mon, 23 Apr 2018 17:27:09 GMT Subject: Re: [PATCH v1 3/5] mem-pool: fill out functionality Message-ID: <898c0b43-b090-fb1f-45d5-ea4041843cdb@gmail.com> In-Reply-To: <20180420162136.144ac5529072f22067abb3b9@google.com> On 04/20/2018 07:21 PM, Jonathan Tan wrote: > On Tue, 17 Apr 2018 16:34:42 +0000 > Jameson Miller wrote: > >> @@ -19,8 +19,27 @@ struct mem_pool { >> >> /* The total amount of memory allocated by the pool. */ >> size_t pool_alloc; >> + >> + /* >> + * Array of pointers to "custom size" memory allocations. >> + * This is used for "large" memory allocations. >> + * The *_end variables are used to track the range of memory >> + * allocated. >> + */ >> + void **custom, **custom_end; >> + int nr, nr_end, alloc, alloc_end; > > 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/