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dm io: use fixed initial mempool size

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Replace the arbitrary calculation of an initial io struct mempool size
with a constant.

The code calculated the number of reserved structures based on the request
size and used a "magic" multiplication constant of 4.  This patch changes
it to reserve a fixed number - itself still chosen quite arbitrarily.
Further testing might show if there is a better number to choose.

Note that if there is no memory pressure, we can still allocate an
arbitrary number of "struct io" structures.  One structure is enough to
process the whole request.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka
2011-05-29 13:03:09 +01:00
committed by Alasdair G Kergon
parent d04714580f
commit bda8efec5c
6 changed files with 10 additions and 41 deletions
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13
drivers/md/dm-snap-persistent.c
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@@ -154,11 +154,6 @@ struct pstore {
struct workqueue_struct *metadata_wq;
};
static unsigned sectors_to_pages(unsigned sectors)
{
return DIV_ROUND_UP(sectors, PAGE_SIZE >> 9);
}
static int alloc_area(struct pstore *ps)
{
int r = -ENOMEM;
@@ -318,8 +313,7 @@ static int read_header(struct pstore *ps, int *new_snapshot)
chunk_size_supplied = 0;
}
ps->io_client = dm_io_client_create(sectors_to_pages(ps->store->
chunk_size));
ps->io_client = dm_io_client_create();
if (IS_ERR(ps->io_client))
return PTR_ERR(ps->io_client);
@@ -368,11 +362,6 @@ static int read_header(struct pstore *ps, int *new_snapshot)
return r;
}
r = dm_io_client_resize(sectors_to_pages(ps->store->chunk_size),
ps->io_client);
if (r)
return r;
r = alloc_area(ps);
return r;