Re: [RFT] Support for ~2144 SCSI discs

Richard Gooch (rgooch@ras.ucalgary.ca)
Tue, 31 Jul 2001 08:25:45 -0400


Jeremy Higdon writes:
> With the sard patch and a 64 bit system, you start having
> trouble at around 103 configured disks, because of the following

So even without my patch, sard doesn't support the previous limit of
128 devices.

> line in sd_init() (sd.c), because kmalloc doesn't like allocating
> large chunks of memory:
>
> sd = kmalloc((sd_template.dev_max << 4) *
> sizeof(struct hd_struct),
> GFP_ATOMIC);
>
> Without sard, you'd have problems past 512 disks.

Yes, when I was coding up the patch I noticed the use of GFP_ATOMIC in
the allocation calls. I have two questions:
- can we use GFP_KERNEL instead (why use GFP_ATOMIC)
- can we switch to vmalloc() instead of kmalloc()?

> With the sard patch, the hd_struct looks like the following:
>
> struct hd_struct {
> long start_sect;
> long nr_sects;
> devfs_handle_t de; /* primary (master) devfs entry */
>
> int number; /* stupid old code wastes space */
>
> /* Performance stats: */
> unsigned int ios_in_flight;
> unsigned int io_ticks;
> unsigned int last_idle_time;
> unsigned int last_queue_change;
> unsigned int aveq;
>
> unsigned int rd_ios;
> unsigned int rd_merges;
> unsigned int rd_ticks;
> unsigned int rd_sectors;
> unsigned int wr_ios;
> unsigned int wr_merges;
> unsigned int wr_ticks;
> unsigned int wr_sectors;
> };
>
> The caveat is that I'm looking at a patch that is a few months old (I
> couldn't find where the latest version of the kernel patch is).

Do the stats have to be kept on a per-partition basic? What about
per-device instead?

Regards,

Richard....
Permanent: rgooch@atnf.csiro.au
Current: rgooch@ras.ucalgary.ca
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