Hi Steven,
Thank you for your answer,
Le Mon, 14 Jan 2008 14:18:54 +0000,
Steven Whitehouse <swhiteho@xxxxxxxxxx> a écrit :
> Basically yes. It reads all the RGs, although in the allocation case
> it doesn't need to read all the RGs to work out where to put newly
> allocated blocks, it only needs to read some of them. That also needs
> to be fixed at some stage in the future.
>
If i trust the code (and i _do_ trust the code :-) )
cluster-1.03, rgrp.c , L1193,
--
static int
get_local_rgrp(struct gfs_inode *ip)
{
(...)
for (;;) {
error = gfs_glock_nq_init(rgd->rd_gl,
LM_ST_EXCLUSIVE, flags,
&al->al_rgd_gh);
switch (error) {
case 0:
if (try_rgrp_fit(rgd, al))
goto out;
gfs_glock_dq_uninit(&al->al_rgd_gh);
break;
--
When the FS is freshly formated, we should return quite instantly from
this function; however, that's not the behaviour i observed. What am i
getting wrong ?
> RGs are limited to 2^32 blocks, including the RG header. Generally you
> want to use a number or RGs >> number of nodes. Provided this is true
> then you can make the RGs as large as you like (up to the 2^32 block
> limit) without compromising performance.
>
Then i guess the attached patch could help having RG sized more than
2G.
The patch is not complete: the 2^32 block limit is not expressed
correctly, although it proved to work on a cluster of 6 64bits nodes,
with RG sizes of 4G and 8G and 16G on a 1T FS. In those cases, i got 256
and 128 and 64 RGs. Are those numbers respecting the constraint :
"RGs >> number of nodes,"
as you expressed it ?
(I guess it depends on the usage of the FS : lots
of cross-accesses from one node to other nodes' file , or at the other
side all nodes working mostly on their own files/directories ?)
> Steve.
>
--
Mathieu
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Index: cluster/gfs/gfs_mkfs/main.c
===================================================================
--- cluster/gfs/gfs_mkfs/main.c ()
+++ cluster/gfs/gfs_mkfs/main.c (copie de travail)
@@ -333,12 +333,12 @@
if (comline.expert)
{
- if (1 > comline.rgsize || comline.rgsize > 2048)
+ if (1 > comline.rgsize)
die("bad resource group size\n");
}
else
{
- if (32 > comline.rgsize || comline.rgsize > 2048)
+ if (32 > comline.rgsize)
die("bad resource group size\n");
}
Index: cluster/gfs/gfs_mkfs/mkfs_gfs.h
===================================================================
--- cluster/gfs/gfs_mkfs/mkfs_gfs.h ()
+++ cluster/gfs/gfs_mkfs/mkfs_gfs.h (copie de travail)
@@ -101,7 +101,7 @@
uint32 seg_size; /* The journal segment size */
uint32 journals; /* Number of journals */
uint32 jsize; /* Size of journals */
- uint32 rgsize; /* The Resource Group size */
+ uint64 rgsize; /* The Resource Group size */
int debug; /* Print out debugging information? */
int quiet; /* No messages */
--
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