[Tmem-users] Experiments with Tmem and trying to find out Tmem USAGE statistics

[Icarus Sonic]

1. Experiment data - does it conform to your expectation?

Hi, I've installed on a Dell Optilex GX260(32bit x86 , 1G Memory) Xen-4.0.0
and linux-2.6.18.8-xen kernel dom0 with tmem patched and PRECACHE/PRESWAP
opened.

I did the following experiments and found that tmem does work: I wrote a c
program that touch each page of a 512M 'unsigned char' array, and measured
its running time in dom0. I tried it with three different settings. The
result shows that tmem works but introduce a little bit overhead. Experiment
result is listed as followed:

*Setting 1: tmem off(by booting xen without 'tmem' argument), dom0 with all
available memory close to 1024GB.
Setting 2: tmem off(by booting xen without 'tmem' argument), dom0 with only
256MB memory. xen argument: dom0_mem=256M
Setting 3: tmem on, dom0 with only 256MB memory. xen argument: dom0_mem=256M
tmem

With each setting, I ran it three times. Run time is listed in
[real],[user],[sys] format

Results
**==========================================
**Setting1: **round1(1.503,0.025,1.466), round2(1.487,0.030,1.456),
round3(1.486,0.039,1.444)*
*Setting2: round1(16.591,0.036,2.779), round2(10.434,0.022,2.368)
round3(13.262,0.033,2.305)
**Setting3: round1(8.739,0.035,4.616), round2(4.582,0.036,2.852),
round3(4.604,0.043,3.592)

*With setting 2,run time is 10x of that with setting 1, which is caused by
swapping. Results in setting 3 demostrate that tmem alleviate swapping
problem but introduced overhead.


2. Question: Where can i found how much tmem is used by a domain, and how
much tmem is available?
Tried xm tmem-list -a | xen-tmem-list-parse to see statistics of tmem usage,
its output:

total tmem ops=93859 (errors=91550) -- tmem pages avail=0
datastructs: objs=0 (max=0) pgps=0 (max=0) nodes=0 (max=0)
misc: failed_copies=0 alloc_failed=0 alloc_page_failed=0 low_mem=0
evicted=0/0 relinq=0/0, max_evicts_per_relinq=0, flush_pools=0, eph_count=0,
eph_max=0
domid0:
weight=0,cap=0,compress=0,frozen=0,total_cycles=61882224,succ_eph_gets=0,succ_pers_puts=0,succ_pers_gets=0,eph_count=0,max_eph=0,compression
ratio=0% (samples=0,poor=0,nomem=0)
domid0,id0[EP]:pgp=0(max=0) obj=0(0) objnode=0(0) puts=0/0/0(dup=0/0)
gets=0/0(0%) flush=0/0 flobj=0/0
domid0,id1[EP]:pgp=0(max=0) obj=0(0) objnode=0(0) puts=0/0/0(dup=0/0)
gets=0/0(0%) flush=0/0 flobj=0/0
domid0,id2[PP]:pgp=0(max=0) obj=0(0) objnode=0(0) puts=0/0/0(dup=0/0)
gets=0/0(0%) flush=0/0 flobj=0/0
failed get cycles: avg=642, max=18856, min=384, samples=91550
flush cycles: avg=785, max=2812, min=668, samples=1966
flush_obj cycles: avg=4623, max=12508, min=696, samples=334

But it does not tell me how much tmem is used by a domain or how much tmem
is available in hypervisor?
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