Hi,
Can anybody provide any inputs/suggestions/improvements on the following.
According to my experiments these proved to be a useful utility during low
memory condition on the embedded devices.
Is there something wrong I am doing?
Please provide your suggestions.
Thanks,
Pintu
>________________________________
> From: PINTU KUMAR <pintu_agar...@yahoo.com>
>To: "linux...@kvack.org" <linux...@kvack.org>; "linux-kernel@vger.kernel.org"
><linux-kernel@vger.kernel.org>
>Cc: "linux-arm-ker...@lists.infradead.org"
><linux-arm-ker...@lists.infradead.org>; "pint...@samsung.com"
><pint...@samsung.com>; Anton Vorontsov <anton.voront...@linaro.org>; Alan Cox
><a...@lxorguk.ukuu.org.uk>; richard -rw- weinberger
><richard.weinber...@gmail.com>; "patc...@linaro.org" <patc...@linaro.org>; Mel
>Gorman <mgor...@suse.de>; Wanpeng Li <liw...@linux.vnet.ibm.com>
>Sent: Sunday, 13 January 2013 9:02 PM
>Subject: Introducing Aggressive Low Memory Booster [1]
>
>
>Hi,
>
>
>Here I am trying to introduce a new feature in kernel called "Aggressive Low
>Memory Booster".
>The main advantage of this will be to boost the available free memory of the
>system to "certain level" during extremely low memory condition.
>
>
>Please provide your comments to improve further.
>Can it be used along with vmpressure_fd ???
>
>
>
>It can be invoked as follows:
> a) Automatically by kernel memory management when the memory threshold
>falls below 10MB.
> b) From user space program/scripts by passing the "required amount of
>memory to be reclaimed".
> Example: echo 100 > /dev/shrinkmem
> c) using sys interface - /sys/kernel/debug/shrinkallmem
> d) using an ioctl call and returning number of pages reclaimed.
> e) using a new system call - shrinkallmem(&nrpages);
> f) During CMA to reclaim and shrink a specific CMA regions.
>
>
>
>I have developed a kernel module to verify the (b) part.
>
>
>Here is the snapshot of the write call:
>+static ssize_t shrinkmem_write(struct file *file, const char *buff,
>+ size_t length, loff_t *pos)
>+{
>+ int ret = -1;
>+ unsigned long memsize = 0;
>+ unsigned long nr_reclaim = 0;
>+ unsigned long pages = 0;
>+ ret = kstrtoul_from_user(buff, length, 0, &memsize);
>+ if (ret < 0) {
>+ printk(KERN_ERR "[SHRINKMEM]: kstrtoul_from_user: Failed
>!\n");
>+ return
-1;
>+ }
>+ printk(KERN_INFO "[SHRINKMEM]: memsize(in MB) = %ld\n",
>+ (unsigned long)memsize);
>+ memsize = memsize*(1024UL*1024UL);
>+ nr_reclaim = memsize / PAGE_SIZE;
>+ pages = shrink_all_memory(nr_reclaim);
>+ printk(KERN_INFO "<SHRINKMEM>: Number of Pages Freed: %lu\n", pages);
>+ return pages;
>+}
>Please note: This requires CONFIG_HIBERNATION to be permanently enabled in the
>kernel.
>
>
>Several experiments have been performed on Ubuntu(kernel 3.3) to verify it
>under low memory conditions.
>
>
>Following are some results obtained:
>-------------------------------------
>
>Node 0, zone DMA 290 115 0 0 0 0 0 0
> 0 0 0
>Node 0, zone Normal 304 540 116 13 2 2 0 0
> 0 0 0
>=========================
> total
used free shared buffers cached
>Mem: 497 487 10 0 63 303
>-/+ buffers/cache: 120 376
>Swap: 1458 34 1424
>Total: 1956 522 1434
>=========================
>Total Memory Freed: 342 MB
>Total Memory Freed: 53 MB
>Total
Memory Freed: 23 MB
>Total Memory Freed: 10 MB
>Total Memory Freed: 15 MB
>Total Memory Freed: -1 MB
>Node 0, zone DMA 6 6 7 8 10 9 7 4
> 1 0 0
>Node 0, zone Normal 2129 2612 2166 1723 1260 759 359 108
> 10 0 0
>=========================
> total
used free shared buffers cached
>Mem: 497 47 449 0 0 5
>-/+ buffers/cache: 41 455
>Swap: 1458 97 1361
>Total: 1956 145 1811
>=========================
>
>
>It was verified using a sample shell script "reclaim_memory.sh" which keeps
>recovering memory by doing "echo 500 > /dev/shrinkmem" until no further
>reclaim is possible.
>
>
>The experiments were performed with various scenarios as follows:
>a) Just after the boot up - (could recover around 150MB with 512MB RAM)
>b) After running many applications include youtube videos, large tar files
>download -
>
> [until free mem becomes < 10MB]
> [Could recover around 300MB in one shot]
>c) Run reclaim, while download is in progress and video still playing - (Not
>applications killed)
>
>d) revoke all background applications again, after running reclaim - (No
>impact, normal behavior)
> [Just it took little extra time to launch, as if it was launched for first
>time]
>
>
>
>
>Please see more discussions on this in the last year mailing list:
>
>https://lkml.org/lkml/2012/4/15/35
>
>
>
>Thank You!
>With regards,
>Pintu Kumar
>Samsung - India
>
>
>
>
>
>
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