Commit adb93af4 authored by Ramon Nou's avatar Ramon Nou
Browse files

async writes

parent 01a86b08

CHANGELOG.md

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@@ -7,6 +7,9 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). 


## [Unreleased]

### New

  - Client-side asynchronous write cache with async flushing ([!306](https://storage.bsc.es/gitlab/hpc/gekkofs/-/merge_requests/306))

    - Added client-side asynchronous write caching for data writes to improve IO500 performance.

    - Introduced new environment variable: `LIBGKFS_ASYNC_WRITE`.

  - Metadata batching ([!305](https://storage.bsc.es/gitlab/hpc/gekkofs/-/merge_requests/305))

    - Added client-side metadata batching for file/node creation to reduce metadata RPC bottlenecks.

    - Introduced new environment variables: `LIBGKFS_METADATA_BATCH` and `LIBGKFS_METADATA_BATCH_THRESHOLD`.

README.md

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@@ -703,6 +703,7 @@ Client-metrics require the CMake argument `-DGKFS_ENABLE_CLIENT_METRICS=ON` (see 
- `LIBGKFS_READ_INLINE_PREFETCH` - Prefetch inline data when opening files (default: OFF).

- `LIBGKFS_USE_DIRENTS_COMPRESSION` - Enable compression for directory entries (default: OFF).

- `LIBGKFS_DIRENTS_BUFF_SIZE` - Buffer size for directory entries (default: 8MB).

- `LIBGKFS_ASYNC_WRITE` - Enable client-side asynchronous write cache (default: OFF).

- `GKFS_FUSE_ENTRY_TIMEOUT` - Caching timeout for dentry entries in the FUSE client (default: 1.0).

- `GKFS_FUSE_ATTR_TIMEOUT` - Caching timeout for file attributes in the FUSE client (default: 1.0).

- `GKFS_FUSE_NEGATIVE_TIMEOUT` - Caching timeout for negative lookups in the FUSE client (default: 1.0).
@@ -746,6 +747,11 @@ Remaining buffered creation requests are automatically flushed when the applicat 
- `LIBGKFS_METADATA_BATCH=ON` - Enable client-side metadata batching for file creation (default: OFF).

- `LIBGKFS_METADATA_BATCH_THRESHOLD` - Set the number of file creation operations per host after which the batch is flushed (default: 64).



##### Asynchronous write cache

During write/pwrite operations, when the asynchronous write cache is enabled, the data writes are enqueued on the client side and return immediately. A background worker thread handles sending the writes asynchronously to the daemons. The pending writes are flushed and waited on during `close()`, `fsync()`, or client process teardown.



- `LIBGKFS_ASYNC_WRITE=ON` - Enable client-side asynchronous write caching for data writes (default: OFF).



### Daemon

#### Core

- `GKFS_DAEMON_CREATE_CHECK_PARENTS` - Enable checking parent directory for existence before creating children.

include/client/env.hpp

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@@ -98,6 +98,7 @@ static constexpr auto ENABLE_FORK = ADD_PREFIX("ENABLE_FORK"); 
static constexpr auto METADATA_BATCH = ADD_PREFIX("METADATA_BATCH");

static constexpr auto METADATA_BATCH_THRESHOLD =

        ADD_PREFIX("METADATA_BATCH_THRESHOLD");

static constexpr auto ASYNC_WRITE = ADD_PREFIX("ASYNC_WRITE");



} // namespace gkfs::env

include/client/preload_context.hpp

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@@ -42,6 +42,10 @@ 


#include <map>

#include <unordered_map>

#include <queue>

#include <future>

#include <thread>

#include <condition_variable>

#include <thallium.hpp>

#include <memory>

#include <vector>
@@ -52,6 +56,17 @@ 


#include <bitset>



namespace gkfs::preload {

struct WriteTask {

    std::string path;

    std::vector<char> buf;

    off64_t offset;

    size_t count;

    int8_t num_replicas;

    std::shared_ptr<std::promise<std::pair<int, long>>> promise;

};

} // namespace gkfs::preload



/* Forward declarations */

namespace gkfs {

namespace filemap {
@@ -163,6 +178,14 @@ private: 
            metadata_batch_buffer_;

    mutable std::mutex metadata_batch_mutex_;



    bool use_async_write_{false};

    std::queue<WriteTask> async_write_queue_;

    std::vector<std::future<std::pair<int, long>>> async_write_futures_;

    std::mutex async_write_mutex_;

    std::condition_variable async_write_cv_;

    std::thread async_write_thread_;

    bool async_write_stop_{false};





public:

    static PreloadContext*
@@ -404,6 +427,28 @@ public: 
    void

    add_metadata_batch_entry(uint64_t host_id, const std::string& path,

                             mode_t mode);



    bool

    use_async_write() const;



    void

    use_async_write(bool use_async_write);



    void

    start_async_write_thread();



    void

    stop_async_write_thread();



    void

    async_write_worker();



    void

    enqueue_async_write(const std::string& path, const void* buf,

                        off64_t offset, size_t count, int8_t num_copies);



    void

    wait_async_writes();

};



} // namespace preload

src/client/gkfs_data.cpp

+19 −0
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@@ -277,6 +277,17 @@ gkfs_do_write(gkfs::filemap::OpenFile& file, const char* buf, size_t count, 
        }

    }



    if(CTX->use_async_write()) {

        CTX->enqueue_async_write(*path, buf, offset, count, 0);

        if(num_replicas > 0) {

            CTX->enqueue_async_write(*path, buf, offset, count, num_replicas);

        }

        if(update_pos) {

            file.pos(offset + count);

        }

        return count;

    }



    pair<int, long> ret_write;

    if(gkfs::config::proxy::fwd_io && CTX->use_proxy() &&

       count > gkfs::config::proxy::fwd_io_count_threshold) {
@@ -592,6 +603,9 @@ gkfs_do_read(const gkfs::filemap::OpenFile& file, char* buf, size_t count, 
ssize_t

gkfs_read_ws(const gkfs::filemap::OpenFile& file, char* buf, size_t count,

             off64_t offset) {

    if(CTX->use_async_write()) {

        CTX->wait_async_writes();

    }

#ifdef GKFS_ENABLE_CLIENT_METRICS

    auto start_t = std::chrono::high_resolution_clock::now();

    auto read = gkfs_do_read(file, buf, count, offset);
@@ -724,6 +738,11 @@ gkfs_fsync(unsigned int fd) { 
        errno = EBADF;

        return -1;

    }



    if(CTX->use_async_write()) {

        CTX->wait_async_writes();

    }



    // flush write size cache to be server consistent

    if(CTX->use_write_size_cache()) {

        auto err = CTX->write_size_cache()->flush(file->path(), true).first;