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Date: Tue, 15 Sep 2015 16:38:01 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To: Vitaly Wool <vitalywool@...il.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
minchan@...nel.org, linux-mm@...ck.org,
sergey.senozhatsky@...il.com, linux-kernel@...r.kernel.org,
ddstreet@...e.org
Subject: Re: [PATCH 1/3] zram: make max_zpage_size configurable
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@...il.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@...are.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
> > >
> > > --
> > > To unsubscribe, send a message with 'unsubscribe linux-mm' in
> > > the body to [4]majordomo@...ck.org. For more info on Linux MM,
> > > see: [5]http://www.linux-mm.org/ .
> > > Don't email: <a href=mailto:"[6]dont@...ck.org"> [7]email@...ck.org
> </a>
> > >
>
> References
>
> Visible links
> 1. mailto:sergey.senozhatsky.work@...il.com
> 2. mailto:vitalywool@...il.com
> 3. mailto:ngupta@...are.org
> 4. mailto:majordomo@...ck.org
> 5. http://www.linux-mm.org/
> 6. mailto:dont@...ck.org
> 7. mailto:email@...ck.org
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