Date: Thu, 1 Jul 2010 13:33:57 -0500 From: Alan Cox <alan.l.cox@gmail.com> To: Jeseem S <jeseems@gmail.com> Cc: freebsd-current@freebsd.org Subject: Re: tmpfs use of wired_count Message-ID: <AANLkTikVMsZ13BWI_yhQqdwI8ZNhMZWHb-w5mL50hk1Z@mail.gmail.com> In-Reply-To: <AANLkTimaRHB7ac8QbHdzE8t_Uekm34WwOx-aw14IK1AB@mail.gmail.com> References: <AANLkTimaRHB7ac8QbHdzE8t_Uekm34WwOx-aw14IK1AB@mail.gmail.com>
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On Wed, Jun 30, 2010 at 11:33 AM, Jeseem S <jeseems@gmail.com> wrote:
> hi,
> I am a newbie on freebsd kernel. Am currently trying to debug a scenario,
> where a custom driver I load uses a lot of static memory and hence lots of
> wired pages.
> The system still has a lot of free memory ( more than 200MB) and a free
> swap
> space ( > 500MB).
> Once I load the driver, the tmpfs loaded on /tmp shows a size of 0.
>
> in tmpfs/tmpfs.h, I see that the free memory available is reduced by number
> of wired pages ( see code below).
> Is this correct logic ? why do we need to reduce wired count from free
> pages available ?
>
>
No, it doesn't appear correct. Moreover, it's also incorrect that
cnt.v_cache_count isn't included in the initial calculation of size.
Regards,
Alan
>
> /*
> * Returns information about the number of available memory pages,
> * including physical and virtual ones.
> *
> * If 'total' is TRUE, the value returned is the total amount of memory
> * pages configured for the system (either in use or free).
> * If it is FALSE, the value returned is the amount of free memory pages.
> *
> * Remember to remove TMPFS_PAGES_RESERVED from the returned value to avoid
> * excessive memory usage.
> *
> */
> static __inline size_t
> tmpfs_mem_info(void)
> {
> size_t size;
>
> size = swap_pager_avail + cnt.v_free_count + cnt.v_inactive_count;
> size -= size > cnt.v_wire_count ? cnt.v_wire_count : size;
> return size;
> }
>
>
> Thanks
> Jeseem
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