Re: [PATCH 1/3] zram: make max_zpage_size configurable

Sergey Senozhatsky
2015-09-15T07:37:18Z

On (09/15/15 09:18), Vitaly Wool wrote:
> > On (09/14/15 15:50), Vitaly Wool wrote:
> > > It makes sense to have control over what compression ratios are
> > > ok to store pages uncompressed and what not.
> >
> > um... I don't want this to be exported. this is very 'zram-internal'.
> >
> > besides, you remove the exsiting default value
> > - static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
> >
> > so now people must provide this module param in order to make zram
> > work the way it used to work for years?
> >
>
> I do not remove it, I move it :) May I ask to review the patch again
> please?

Oh, yep, missed that.

Please read Dan Streetman's reply. I agree with what he said/suggested.

And can you please switch your email client to 'plain text' mode only?
haven't checked, but I suspect that some of vger lists block !plain_text
emails. ... apart from the fact that it's hard to read such emails in
mutt, etc.

-ss

> >
> > > Moreover, if we end up using zbud allocator for zram, any attempt to
> > > allocate a whole page will fail, so we may want to avoid this as much
> > > as possible.
> >
> > so how does it help?
> >
> > > So, let's have max_zpage_size configurable as a module parameter.
> > >
> > > Signed-off-by: Vitaly Wool <[2]vitalywool@gmail.com>
> > > ---
> > >  drivers/block/zram/zram_drv.c | 13 +++++++++++++
> > >  drivers/block/zram/zram_drv.h | 16 ----------------
> > >  2 files changed, 13 insertions(+), 16 deletions(-)
> > >
> > > diff --git a/drivers/block/zram/zram_drv.c
> b/drivers/block/zram/zram_drv.c
> > > index 9fa15bb..6d9f1d1 100644
> > > --- a/drivers/block/zram/zram_drv.c
> > > +++ b/drivers/block/zram/zram_drv.c
> > > @@ -42,6 +42,7 @@ static const char *default_compressor = "lzo";
> > >
> > >  /* Module params (documentation at end) */
> > >  static unsigned int num_devices = 1;
> > > +static size_t max_zpage_size = PAGE_SIZE / 4 * 3;
> > >
> > >  static inline void deprecated_attr_warn(const char *name)
> > >  {
> > > @@ -1411,6 +1412,16 @@ static int __init zram_init(void)
> > >               return ret;
> > >       }
> > >
> > > +     /*
> > > +      * max_zpage_size must be less than or equal to:
> > > +      * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
> > > +      * always return failure.
> > > +      */
> > > +     if (max_zpage_size > PAGE_SIZE) {
> > > +             pr_err("Invalid max_zpage_size %ld\n", max_zpage_size);
> >
> > and how do people find out ZS_MAX_ALLOC_SIZE? this error message does
> not
> > help.
> >
> > > +             return -EINVAL;
> > > +     }
> > > +
> > >       zram_major = register_blkdev(0, "zram");
> > >       if (zram_major <= 0) {
> > >               pr_err("Unable to get major number\n");
> > > @@ -1444,6 +1455,8 @@ module_exit(zram_exit);
> > >
> > >  module_param(num_devices, uint, 0);
> > >  MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices");
> > > +module_param(max_zpage_size, ulong, 0);
> > > +MODULE_PARM_DESC(max_zpage_size, "Threshold for storing compressed
> pages");
> >
> > unclear description.
> >
> >
> > >
> > >  MODULE_LICENSE("Dual BSD/GPL");
> > >  MODULE_AUTHOR("Nitin Gupta <[3]ngupta@vflare.org>");
> > > diff --git a/drivers/block/zram/zram_drv.h
> b/drivers/block/zram/zram_drv.h
> > > index 8e92339..3a29c33 100644
> > > --- a/drivers/block/zram/zram_drv.h
> > > +++ b/drivers/block/zram/zram_drv.h
> > > @@ -20,22 +20,6 @@
> > >
> > >  #include "zcomp.h"
> > >
> > > -/*-- Configurable parameters */
> > > -
> > > -/*
> > > - * Pages that compress to size greater than this are stored
> > > - * uncompressed in memory.
> > > - */
> > > -static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
> > > -
> > > -/*
> > > - * NOTE: max_zpage_size must be less than or equal to:
> > > - *   ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
> > > - * always return failure.
> > > - */
> > > -
> > > -/*-- End of configurable params */
> > > -
> > >  #define SECTOR_SHIFT         9
> > >  #define SECTORS_PER_PAGE_SHIFT       (PAGE_SHIFT - SECTOR_SHIFT)
> > >  #define SECTORS_PER_PAGE     (1 << SECTORS_PER_PAGE_SHIFT)
> > > --
> > > 1.9.1
> > >
> > > --
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>
> > >
>
> References
>
> Visible links
> 1. mailto:sergey.senozhatsky.work@gmail.com
> 2. mailto:vitalywool@gmail.com
> 3. mailto:ngupta@vflare.org
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