Lookup is repeated after request is identified as miss and hash bucket
lock is upgraded (in order to map missing cachelines). At this point
cachelines status might change and the request might turn out to be
a hit after all. Adding check for this condition removes unnecessary
calls to remap logic.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
update_req_info() should include REMAPPED cachelines
in repart stats (number of cachelines within request
belonging to other than the target partition).
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Removing conditional early return from engine_map() function
in case of insufficient free cachelines. The reasons are:
1. current implementation does not treat unssufficient free
cachelines condition as an error,
2. the check is based on stale request info, so it is inaccurate,
3. it is easier to hit more paths with functional tests,
4. partially mapping request from the freelist becomes more common
rather than being a corner case dependent on racy timings between
threads
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
set_hot() depends on cacheline metadata status to determine
on which list the element is located (dirty cs clean list).
Thus at least hash bucket lock is required when calling
set_hot().
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Early return from engine_map() in case of insufficient free
cachelines on the freelist is opportunistic, as both request
map info and freelist count are not accurate. Map info is stale
as it is to be refreshed in engine_map() after hash bucket
lock had been upgraded. Freelist count on other hand is subject
to change asynchronously.
The implementation assumption however is that after engine_map()
request is fully traversed (engine_map() is equivalent to
engine_lookup() followed by an attempt to map missing cachelines).
So in case of early return we must take care of repeating the
lookup.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
At this point cacheline status in request map is stale,
as lookup was performed before upgrading hash bucket lock.
If indeed all cachelines are mapped, this will be determined
in the main loop of engine_map().
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
This assures that cacheline with LOOKUP_INSERTED status
is always present on the LRU list.
This fixes an ENV_BUG() caused by an attempt to remove
a cacheline from LRU list which was not there. This
happened when cacheline was mapped from freelist
(LOOKUP_INSERTED) but the entire request mapping failed
and generic cleanup routines attempted to invalidate cacheline,
including removing it from the LRU list. As engine_set_hot()
is called after successfull mapping, the inserted cacheline was
not yet present on the LRU list.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Split traversation into two distinct phases: lookup()
and lru set_hot(). prepare_cachelines() now only calls
set_hot() once after lookup and insert are finished.
lookup() is called explicitly only once in
prepare_cachelines() at the very beginning of the
procedure. If request is a miss then then map()
performs operations equivalent to lookup() supplemented
by an attempt to map cachelines. Both lookup() and
set_hot() are called via traverse() from the engines
which do not attempt mapping, and thus do not call
prepare_clines().
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Unmapping cachelines previously mapped from freelist before
eviction is a waste of resources. Also if map does not erarly
exit upon first mapping error, we can have request fully
traversed (and partially mapped) after mapping and thus
skip lookup in eviction.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Eviction changes allowing to evict (remap) cachelines while
holding hash bucket write lock instead of global metadata
write lock.
As eviction (replacement) is now tightly coupled with request,
each request uses eviction size equal to number of its
unmapped cachelines.
Evicting without global metadata write lock is possible
thanks to the fact that remaping is always performed
while exclusively holding cacheline (read or write) lock.
So for a cacheline on LRU list we acquire cacheline lock,
safely resolve hash and consequently write-lock hash bucket.
Since cacheline lock is acquired under hash bucket (everywhere
except for new eviction implementation), we are certain that
noone acquires cacheline lock behind our back. Concurrent
eviction threads are eliminated by holding eviction list
lock for the duration of critial locking operations.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
.. so that the main part, responsible strictly for mapping
given LBA to given collision index, is encapsulated in
a function ocf_map_cache_line with external linkage.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Changing sequential request detection so that a miss request is
recognized as sequential after needed cachelines are evicted
and mapped to the request in a sequential order.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
.. to make it clean that true means cleaner must lock
cachelines rather than the lock is already being held.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Allowing request cacheline lock to be called on partially
locked request. This is going to be usefull for upcomming
eviction improvements, where request will first have evicted
(LOOKUP_REMAPPED) cachelines assigned to it in a locked state,
followed by standard request cacheline lock call in order to
lock previously inserted (LOOKUP_HIT) or mapped from freelist
(LOOKUP_INSERTED) cachelines.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Cacheline concurrency functions have their interface changed
so that the cacheline concurrency private context is
explicitly on the parameter list, rather than being taken
from cache->device->concurrency.cache_line.
Cache pointer is no longer provided as a parameter to these
functions. Cacheline concurrency context now has a pointer
to cache structure (for logging purposes only).
The purpose of this change is to facilitate unit testing.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
1. new abbreviated previx: ocf_hb (HB stands for hash bucket)
2. clear distinction between functions requiring caller to
hold metadata shared global lock ("naked") vs the ones
which acquire global lock on its own ("prot" for protected)
3. clear distinction between hash bucket locking functions
accepting hash bucket id ("id"), core line and lba ("cline")
and entire request ("req").
Resulting naming scheme:
ocf_hb_(id/cline/req)_(prot/naked)_(lock/unlock/trylock)_(rd/wr)
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Removing the logic for oportunistic partition overflow
reduction by evicting more cachelines than actually
required by the request being serviced.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
If request is hit, simply try to acquire cachelines instead of verifying
whether target partition's size is not exceeded.
Signed-off-by: Michal Mielewczyk <michal.mielewczyk@intel.com>
Since the request carries an explicit information about number of the
cacheliens to be reparted, no need of keeping the boolean information if some
of the request's cachelines are assigned to a wrong partition
Signed-off-by: Michal Mielewczyk <michal.mielewczyk@intel.com>
Instead of redunant calculating number of cachlines to be reparted, keep this
information in request's info
Signed-off-by: Michal Mielewczyk <michal.mielewczyk@intel.com>
WA write must follow follow the same two-pass pattern
as WI does. This change modifies WA engine to default to
WI in case of any miss (either partial or full), not only
partial miss.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
Add second pass of write invalidate. It is necessary only
if concurrent I/O had inserted target LBAs to cache after
WI request did traversation. These LBAs might have been
written by WI request behind the concurrent I/O's back,
resulting in making these sectors effectively invalid.
In this case we must update these sectors' metadata to
reflect this. However we won't know about this after we
traverse the request again - hence calling ocf_write_wi
again with req->wi_second_pass set to indicate that this
is the second pass (core write should be skipped).
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
core_id should be set in this function. The fact that
it is missing might lead to incorrect behaviour e.g. in
case of promotion policy.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
In case of partial hit WO engine first reads data for the entire
request address range from core device. Then it plumbs it by fetching
dirty sectors from cache device.
For unindentified reason this leads to a data corruption in YCSB
workload A. After flushing dirty data and re-loading cache the
data is correct.
This change modifies WO read handler to read clean data from the
cache. This is not optimal, as the clean sectors are now read twice
in case of partial hit. For now it seems to be good enough work-around
for the data corruption problem.
The symptoms, combined with the fact that this change seems to make
the problem go away, indicates that at some point WB write handler
(and/or special I/O request handlers like discard) puts CAS in a
state where in-memory medata wrongly indicates that a sector is
clean while in fact it is dirty, as marked in the on-disk metadata.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
