lkml.org 
[lkml]   [2014]   [Apr]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 6/8] idr: avoid ping-pong
Hello,

On Sat, Apr 19, 2014 at 06:43:41PM +0800, Lai Jiangshan wrote:
> On 04/19/2014 01:17 AM, Tejun Heo wrote:
> It only frees one layer. And the ida_pre_get() for the next ida_get_new*()
> will allocation it back again. The aim "Throw away extra resources one by one"
> can't be achieved. It can't keep its memory footprint minimal.

Isn't the point not keeping the memory around per-ida between
allocations which can be arbitrarily long? Why isn't it achieved?

> > I think the right
> > thing to do is implementing ida_preload() which is simliar to
> > idr_preload() and do away with per-ida layer cache.
>
> Yes and no.
>
> We need a static private ida_preload() for ida_simple_get() only.
>
> Because the IDA doesn't have any query-function, so IDA's own synchronization
> is enough for all use cases, IDA should off-loads the caller's
> synchronization burden.

Hmmm? And why can't that use preload on its own?

> In my todo-list, IDA only needs the following functions. other functions
> will be deprecated and scheduled to be removed:
> void ida_destroy(struct ida *ida);
> void ida_init(struct ida *ida);
> int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
> gfp_t gfp_mask);
> void ida_simple_remove(struct ida *ida, unsigned int id);
>
> (I don't think we need any query-function, But...)
> If in the future we need some query-functions such as:
> ida_is_this_id_allocated()
> ida_find_next_[un]allocated_id(),
> In this case, we can expose the ida_preload() and ida_alloc() at the same time that
> we introduce the query-functions.

Regardless of interface, we can still switch to per-cpu layer caching
which would make this per-ida allocation issue go away. I'd much
prefer to see that than debating the (dis)merits of this patch.

Thanks.

--
tejun


\
 
 \ /
  Last update: 2014-04-19 15:21    [W:0.110 / U:0.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site